Now that we have removed the one user of mmap_region() outside of mm, make
it internal and add it to vma.c so it can be userland tested.
This ensures that all external memory mappings are performed using the
appropriate interfaces and allows us to modify memory mapping logic as we
see fit.
Additionally expand test stubs to allow for the mmap_region() code to
compile and be userland testable.
Link: https://lkml.kernel.org/r/de5a3c574d35c26237edf20a1d8652d7305709c9.1735819274.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Introduce demonstrative, basic, __mmap_region() test upon which we can
base further work upon moving forwards.
This simply asserts that mappings can be made and merges occur as
expected.
As part of this change, fix the security_vm_enough_memory_mm() stub which
was previously incorrectly implemented.
Link: https://lkml.kernel.org/r/20241213162409.41498-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Convert mm_lock_seq to be seqcount_t and change all mmap_write_lock
variants to increment it, in-line with the usual seqcount usage pattern.
This lets us check whether the mmap_lock is write-locked by checking
mm_lock_seq.sequence counter (odd=locked, even=unlocked). This will be
used when implementing mmap_lock speculation functions.
As a result vm_lock_seq is also change to be unsigned to match the type
of mm_lock_seq.sequence.
Link: https://lkml.kernel.org/r/20241122174416.1367052-2-surenb@google.com
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This was arbitrarily left in mmap.c it makes no sense being there, move it
to vma.c to render it testable.
Link: https://lkml.kernel.org/r/5e5e81807c54dfbe363edb2d431eb3d7a37fcdba.1733248985.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We build on previous work making expand_downwards() an entirely internal
function.
This logic is subtle and so it is highly useful to get it into vma.c so we
can then userland unit test.
We must additionally move acct_stack_growth() to vma.c as it is a helper
function used by both expand_downwards() and expand_upwards().
We are also then able to mark anon_vma_interval_tree_pre_update_vma() and
anon_vma_interval_tree_post_update_vma() static as these are no longer
used by anything else.
Link: https://lkml.kernel.org/r/0feb104eff85922019d4fb29280f3afb130c5204.1733248985.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We want to be able to unit test the unmapped area logic, so move it to
mm/vma.c. The wrappers which invoke this remain in place in mm/mmap.c.
In addition, naturally, update the existing test code to enable this to be
compiled in userland.
Link: https://lkml.kernel.org/r/53a57a52a64ea54e9d129d2e2abca3a538022379.1733248985.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/vma: make more mmap logic userland testable".
This series carries on the work started in previous series and
continued in commit 52956b0d7fb9 ("mm: isolate mmap internal logic to
mm/vma.c"), moving the remainder of memory mapping implementation
details logic into mm/vma.c allowing the bulk of the mapping logic to
be unit tested.
It is highly useful to do so, as this means we can both fundamentally test
this core logic, and introduce regression tests to ensure any issues
previously resolved do not recur.
Vitally, this includes the do_brk_flags() function, meaning we have both
core means of userland mapping memory now testable.
Performance testing was performed after this change given the brk() system
call's sensitivity to change, and no performance regression was observed.
The stack expansion logic is also moved into mm/vma.c, which necessitates
a change in the API exposed to the exec code, removing the invocation of
the expand_downwards() function used in get_arg_page() and instead adding
mmap_read_lock_maybe_expand() to wrap this.
This patch (of 5):
Now we have moved mmap_region() internals to mm/vma.c, making it available
to userland testing, it makes sense to do the same with brk().
This continues the pattern of VMA heavy lifting being done in mm/vma.c in
an environment where it can be subject to straightforward unit and
regression testing, with other VMA-adjacent files becoming wrappers around
this functionality.
[lorenzo.stoakes@oracle.com: add missing personality header import]
Link: https://lkml.kernel.org/r/2a717265-985f-45eb-9257-8b2857088ed4@lucifer.local
Link: https://lkml.kernel.org/r/cover.1733248985.git.lorenzo.stoakes@oracle.com
Link: https://lkml.kernel.org/r/3d24b9e67bb0261539ca921d1188a10a1b4d4357.1733248985.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently vma test is failing because of the new vma_assert_attached()
assertion. The check is failing because previous refcount_set() inside
vma_mark_attached() is a NoOp. Fix the definition of atomic_set() to
correctly set the value of the atomic.
Link: https://lkml.kernel.org/r/20241227222220.1726384-1-surenb@google.com
Fixes: 9325b8b5a1cb ("tools: add skeleton code for userland testing of VMA logic")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "fix error handling in mmap_region() and refactor", v3.
The mmap_region() function is somewhat terrifying, with spaghetti-like
control flow and numerous means by which issues can arise and incomplete
state, memory leaks and other unpleasantness can occur.
This series goes to great lengths to simplify how mmap_region() works and
to avoid unwinding errors late on in the process of setting up the VMA for
the new mapping, and equally avoids such operations occurring while the
VMA is in an inconsistent state.
This series builds on the previously submitted hotfix patches (see link to
v2 below) which addresses the most critical issues around mmap_region(),
and further works to improve mmap_region() complexity, stability, and
testability.
This series moves the code to mm/vma.c to render it userland testable,
refactors and simplifies it into smaller functions that are significantly
more readable.
It additionally avoids performing an attempt at a second merge mid-way
through allocating a new VMA, a dubious proposition at best and one that
is highly subject to subtle bugs.
Rather than do this, we simply note that we ought to retry the merge and
do this as a final step.
This patch (of 3):
Add some additional vma_internal.h stubs in preparation for
__mmap_region() being moved to mm/vma.c. Without these the move would
result in the tests no longer compiling.
Link: https://lkml.kernel.org/r/cover.1729858176.git.lorenzo.stoakes@oracle.com
Link: https://lkml.kernel.org/r/74b27e159e261d2ac1fe66a130edad1d61fdc176.1729858176.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The phys_addr_t size is predicated on whether CONFIG_PHYS_ADDR_T_64BIT is
set or not.
In the VMA tests, virt_to_phys() from tools/include/linux casts a volatile
void * pointer to phys_addr_t, if CONFIG_PHYS_ADDR_T_64BIT is not set,
this will be 32-bit and trigger a warning.
Obviously this might also lead to truncation, which we would rather avoid.
Fix this by adjusting the generation of generated/bit-length.h to generate
a CONFIG_PHYS_ADDR_T{bits}BIT define.
This does result in the generation of the useless CONFIG_PHYS_ADDR_T_32BIT
define for 32-bit systems, but this should have no effect, and makes
implementation of this easier.
This resolves the issue and the warning.
[lorenzo.stoakes@oracle.com: VMA tests not properly importing bit-length.h]
Link: https://lkml.kernel.org/r/a6183df9-3108-4d59-8128-4fc6c14e22a5@lucifer.local
Link: https://lkml.kernel.org/r/20241017165638.95602-1-lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Tested-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a test to assert that VMG_FLAG_JUST_EXPAND functions as expected - that
is, when the VMA iterator is positioned at the previous VMA and no VMAs
proceed it, we observe an expansion with all state as expected.
Explicitly place a prior VMA that would otherwise fail this test if the
mode were not enabled (as it would traverse to the previous-previous VMA).
Link: https://lkml.kernel.org/r/d2f88330254a6448092412bf7dfe077a579ab0dc.1729174352.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Jann Horn <jannh@google.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In commit 714965ca8252 ("mm/mmap: start distinguishing if vma can be
removed in mergeability test") we relaxed the VMA merge rules for VMAs
possessing a vm_ops->close() hook, permitting this operation in instances
where we wouldn't delete the VMA as part of the merge operation.
This was later corrected in commit fc0c8f9089c2 ("mm, mmap: fix
vma_merge() case 7 with vma_ops->close") to account for a subtle case that
the previous commit had not taken into account.
In both instances, we first rely on is_mergeable_vma() to determine
whether we might be dealing with a VMA that might be removed, taking
advantage of the fact that a 'previous' VMA will never be deleted, only
VMAs that follow it.
The second patch corrects the instance where a merge of the previous VMA
into a subsequent one did not correctly check whether the subsequent VMA
had a vm_ops->close() handler.
Both changes prevent merge cases that are actually permissible (for
instance a merge of a VMA into a following VMA with a vm_ops->close(), but
with no previous VMA, which would result in the next VMA being extended,
not deleted).
In addition, both changes fail to consider the case where a VMA that would
otherwise be merged with the previous and next VMA might have
vm_ops->close(), on the assumption that for this to be the case, all three
would have to have the same vma->vm_file to be mergeable and thus the same
vm_ops.
And in addition both changes operate at 50,000 feet, trying to guess
whether a VMA will be deleted.
As we have majorly refactored the VMA merge operation and de-duplicated
code to the point where we know precisely where deletions will occur, this
patch removes the aforementioned checks altogether and instead explicitly
checks whether a VMA will be deleted.
In cases where a reduced merge is still possible (where we merge both
previous and next VMA but the next VMA has a vm_ops->close hook, meaning
we could just merge the previous and current VMA), we do so, otherwise the
merge is not permitted.
We take advantage of our userland testing to assert that this functions
correctly - replacing the previous limited vm_ops->close() tests with
tests for every single case where we delete a VMA.
We also update all testing for both new and modified VMAs to set
vma->vm_ops->close() in every single instance where this would not prevent
the merge, to assert that we never do so.
Link: https://lkml.kernel.org/r/9f96b8cfeef3d14afabddac3d6144afdfbef2e22.1725040657.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The existing vma_merge() function is no longer required to handle what
were previously referred to as cases 1-3 (i.e. the merging of a new VMA),
as this is now handled by vma_merge_new_vma().
Additionally, simplify the convoluted control flow of the original,
maintaining identical logic only expressed more clearly and doing away
with a complicated set of cases, rather logically examining each possible
outcome - merging of both the previous and subsequent VMA, merging of the
previous VMA and merging of the subsequent VMA alone.
We now utilise the previously implemented commit_merge() function to share
logic with vma_expand() de-duplicating code and providing less surface
area for bugs and confusion. In order to do so, we adjust this function
to accept parameters specific to merging existing ranges.
Link: https://lkml.kernel.org/r/2cf6016b7bfcc4965fc3cde10827560c42e4f12c.1725040657.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Abstract vma_merge_new_vma() to use vma_merge_struct and rename the
resultant function vma_merge_new_range() to be clear what the purpose of
this function is - a new VMA is desired in the specified range, and we
wish to see if it is possible to 'merge' surrounding VMAs into this range
rather than having to allocate a new VMA.
Note that this function uses vma_extend() exclusively, so adopts its
requirement that the iterator point at or before the gap. We add an
assert to this effect.
This is as opposed to vma_merge_existing_range(), which will be introduced
in a subsequent commit, and provide the same functionality for cases in
which we are modifying an existing VMA.
In mmap_region() and do_brk_flags() we open code scenarios where we prefer
to use vma_expand() rather than invoke a full vma_merge() operation.
Abstract this logic and eliminate all of the open-coding, and also use the
same logic for all cases where we add new VMAs to, rather than ultimately
use vma_merge(), rather use vma_expand().
Doing so removes duplication and simplifies VMA merging in all such cases,
laying the ground for us to eliminate the merging of new VMAs in
vma_merge() altogether.
Also add the ability for the vmg to track state, and able to report
errors, allowing for us to differentiate a failed merge from an inability
to allocate memory in callers.
This makes it far easier to understand what is happening in these cases
avoiding confusion, bugs and allowing for future optimisation.
Also introduce vma_iter_next_rewind() to allow for retrieval of the next,
and (optionally) the prev VMA, rewinding to the start of the previous gap.
Introduce are_anon_vmas_compatible() to abstract individual VMA anon_vma
comparison for the case of merging on both sides where the anon_vma of the
VMA being merged maybe compatible with prev and next, but prev and next's
anon_vma's may not be compatible with each other.
Finally also introduce can_vma_merge_left() / can_vma_merge_right() to
check adjacent VMA compatibility and that they are indeed adjacent.
Link: https://lkml.kernel.org/r/49d37c0769b6b9dc03b27fe4d059173832556392.1725040657.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Tested-by: Mark Brown <broonie@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The purpose of the vmg is to thread merge state through functions and
avoid egregious parameter lists. We expand this to vma_expand(), which is
used for a number of merge cases.
Accordingly, adjust its callers, mmap_region() and relocate_vma_down(), to
use a vmg.
An added purpose of this change is the ability in a future commit to
perform all new VMA range merging using vma_expand().
Link: https://lkml.kernel.org/r/4bc8c9dbc9ca52452ef8e587b28fe555854ceb38.1725040657.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Rather than passing around huge numbers of parameters to numerous helper
functions, abstract them into a single struct that we thread through the
operation, the vma_merge_struct ('vmg').
Adjust vma_merge() and vma_modify() to accept this parameter, as well as
predicate functions can_vma_merge_before(), can_vma_merge_after(), and the
vma_modify_...() helper functions.
Also introduce VMG_STATE() and VMG_VMA_STATE() helper macros to allow for
easy vmg declaration.
We additionally remove the requirement that vma_merge() is passed a VMA
object representing the candidate new VMA. Previously it used this to
obtain the mm_struct, file and anon_vma properties of the proposed range
(a rather confusing state of affairs), which are now provided by the vmg
directly.
We also remove the pgoff calculation previously performed vma_modify(),
and instead calculate this in VMG_VMA_STATE() via the vma_pgoff_offset()
helper.
Link: https://lkml.kernel.org/r/a955aad09d81329f6fbeb636b2dd10cde7b73dab.1725040657.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a variety of VMA merge unit tests to assert that the behaviour of VMA
merge is correct at an abstract level and VMAs are merged or not merged as
expected.
These are intentionally added _before_ we start refactoring vma_merge() in
order that we can continually assert correctness throughout the rest of
the series.
In order to reduce churn going forward, we backport the vma_merge_struct
data type to the test code which we introduce and use in a future commit,
and add wrappers around the merge new and existing VMA cases.
Link: https://lkml.kernel.org/r/1c7a0b43cfad2c511a6b1b52f3507696478ff51a.1725040657.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm: remove vma_merge()", v3.
The infamous vma_merge() function has been the cause of a great deal of
pain, bugs and confusion for a very long time.
It is subtle, contains many corner cases, tries to do far too much and is
as a result very fragile.
The fact that the function requires there to be a numbering system to
cover each possible eventuality with references to each in the many
branches of its implementation as to which case you are looking at speaks
to all this.
Some of this complexity is inherent - unfortunately there is no getting
away from the need to figure out precisely how to execute the merge,
whether we need to remove VMAs, whether it is safe to do so, what
constitutes a mergeable VMA and so on.
However, a lot of the complexity is not inherent but instead a product of
the function's 'organic' development.
Liam has gone to great lengths to improve the situation as a part of his
maple tree implementation, greatly improving the readability of the code,
and Vlastimil and myself have additionally gone to lengths to try to
improve things further.
However, with the availability of userland VMA testing, it now becomes
possible to perform a rather more significant refactoring while
maintaining confidence in its correct operation.
An attempt was previously made by Vlastimil [0] to eliminate vma_merge(),
however it was rather - brutal - and an astute reader might refer to the
date of that patch for insight as to its intent.
This series instead divides merge operations into two natural kinds -
merges which occur when a NEW vma is being added to the address space, and
merges which occur when a vma is being MODIFIED.
Happily, the vma_expand() function introduced by Liam, which has the
capacity for also deleting a subsequent VMA, covers each of the NEW vma
cases.
By abstracting the actual final commit of changes to a VMA to its own
function, commit_merge() and writing a wrapper around vma_expand() for new
VMA cases vma_merge_new_range(), we can avoid having to use vma_merge()
for these instances altogether.
By doing so we are also able to then de-duplicate all existing merge logic
in mmap_region() and do_brk_flags() and have everything invoke this new
function, so we universally take the same approach to merging new VMAs.
Having done so, we can then completely rework vma_merge() into
vma_merge_existing_range() and use this for the instances where a merge is
proposed for a region of an existing VMA.
This eliminates vma_merge() and its numbered cases and instead divides
things into logical cases - merge both, merge left, merge right (the
latter 2 being either partial or full merges).
The code is heavily annotated with ASCII diagrams and greatly simplified
in comparison to the existing vma_merge() function.
Having made this change, we take the opportunity to address an issue with
merging VMAs possessing a vm_ops->close() hook - commit 714965ca8252
("mm/mmap: start distinguishing if vma can be removed in mergeability
test") and commit fc0c8f9089c2 ("mm, mmap: fix vma_merge() case 7 with
vma_ops->close") make efforts to relax how we handle these, making
assumptions about which VMAs might end up deleted (and thus, if possessing
a vm_ops->close() hook, cannot be).
This refactor means we do not need to guess, so instead explicitly only
disallow merge in instances where a VMA with a vm_ops->close() hook would
be deleted (and try a smaller merge in cases where this is possible).
In addition to these changes, we introduce a new vma_merge_struct
abstraction to allow VMA merge state to be threaded through the operation
neatly.
There is heavy unit testing provided for all merge functionality, added
prior to the refactoring, allowing for before/after testing.
The vm_ops->close() change also introduces exhaustive testing to
demonstrate that this functions as expected, and in addition to this the
reproduction code from commit fc0c8f9089c2 ("mm, mmap: fix vma_merge()
case 7 with vma_ops->close") was tested and confirmed passing.
[0]:https://lore.kernel.org/linux-mm/20240401192623.18575-2-vbabka@suse.cz/
This patch (of 10):
Have vma.o depend on its source dependencies explicitly, as previously
these were simply being ignored as existing object files were up to date.
This now correctly re-triggers the build if mm/ source is changed as well
as local source code.
Also set clean as a phony rule.
Link: https://lkml.kernel.org/r/cover.1725040657.git.lorenzo.stoakes@oracle.com
Link: https://lkml.kernel.org/r/e3ea58f08364ae5432c9a074de0195a7c7e0b04a.1725040657.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Establish a new userland VMA unit testing implementation under
tools/testing which utilises existing logic providing maple tree support
in userland utilising the now-shared code previously exclusive to radix
tree testing.
This provides fundamental VMA operations whose API is defined in mm/vma.h,
while stubbing out superfluous functionality.
This exists as a proof-of-concept, with the test implementation functional
and sufficient to allow userland compilation of vma.c, but containing only
cursory tests to demonstrate basic functionality.
Link: https://lkml.kernel.org/r/533ffa2eec771cbe6b387dd049a7f128a53eb616.1722251717.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Tested-by: SeongJae Park <sj@kernel.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Gow <davidgow@google.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Kees Cook <kees@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Rae Moar <rmoar@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Pengfei Xu <pengfei.xu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
