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When booting with 'kasan.vmalloc=off', a kernel configured with support for KASAN_HW_TAGS will explode at boot time due to bogus use of virt_to_page() on a vmalloc adddress. With CONFIG_DEBUG_VIRTUAL selected this will be reported explicitly, and with or without CONFIG_DEBUG_VIRTUAL the kernel will dereference a bogus address: | ------------[ cut here ]------------ | virt_to_phys used for non-linear address: (____ptrval____) (0xffff800008000000) | WARNING: CPU: 0 PID: 0 at arch/arm64/mm/physaddr.c:15 __virt_to_phys+0x78/0x80 | Modules linked in: | CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.3.0-rc3-00073-g83865133300d-dirty #4 | Hardware name: linux,dummy-virt (DT) | pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) | pc : __virt_to_phys+0x78/0x80 | lr : __virt_to_phys+0x78/0x80 | sp : ffffcd076afd3c80 | x29: ffffcd076afd3c80 x28: 0068000000000f07 x27: ffff800008000000 | x26: fffffbfff0000000 x25: fffffbffff000000 x24: ff00000000000000 | x23: ffffcd076ad3c000 x22: fffffc0000000000 x21: ffff800008000000 | x20: ffff800008004000 x19: ffff800008000000 x18: ffff800008004000 | x17: 666678302820295f x16: ffffffffffffffff x15: 0000000000000004 | x14: ffffcd076b009e88 x13: 0000000000000fff x12: 0000000000000003 | x11: 00000000ffffefff x10: c0000000ffffefff x9 : 0000000000000000 | x8 : 0000000000000000 x7 : 205d303030303030 x6 : 302e30202020205b | x5 : ffffcd076b41d63f x4 : ffffcd076afd3827 x3 : 0000000000000000 | x2 : 0000000000000000 x1 : ffffcd076afd3a30 x0 : 000000000000004f | Call trace: | __virt_to_phys+0x78/0x80 | __kasan_unpoison_vmalloc+0xd4/0x478 | __vmalloc_node_range+0x77c/0x7b8 | __vmalloc_node+0x54/0x64 | init_IRQ+0x94/0xc8 | start_kernel+0x194/0x420 | __primary_switched+0xbc/0xc4 | ---[ end trace 0000000000000000 ]--- | Unable to handle kernel paging request at virtual address 03fffacbe27b8000 | Mem abort info: | ESR = 0x0000000096000004 | EC = 0x25: DABT (current EL), IL = 32 bits | SET = 0, FnV = 0 | EA = 0, S1PTW = 0 | FSC = 0x04: level 0 translation fault | Data abort info: | ISV = 0, ISS = 0x00000004 | CM = 0, WnR = 0 | swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000041bc5000 | [03fffacbe27b8000] pgd=0000000000000000, p4d=0000000000000000 | Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP | Modules linked in: | CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 6.3.0-rc3-00073-g83865133300d-dirty #4 | Hardware name: linux,dummy-virt (DT) | pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) | pc : __kasan_unpoison_vmalloc+0xe4/0x478 | lr : __kasan_unpoison_vmalloc+0xd4/0x478 | sp : ffffcd076afd3ca0 | x29: ffffcd076afd3ca0 x28: 0068000000000f07 x27: ffff800008000000 | x26: 0000000000000000 x25: 03fffacbe27b8000 x24: ff00000000000000 | x23: ffffcd076ad3c000 x22: fffffc0000000000 x21: ffff800008000000 | x20: ffff800008004000 x19: ffff800008000000 x18: ffff800008004000 | x17: 666678302820295f x16: ffffffffffffffff x15: 0000000000000004 | x14: ffffcd076b009e88 x13: 0000000000000fff x12: 0000000000000001 | x11: 0000800008000000 x10: ffff800008000000 x9 : ffffb2f8dee00000 | x8 : 000ffffb2f8dee00 x7 : 205d303030303030 x6 : 302e30202020205b | x5 : ffffcd076b41d63f x4 : ffffcd076afd3827 x3 : 0000000000000000 | x2 : 0000000000000000 x1 : ffffcd076afd3a30 x0 : ffffb2f8dee00000 | Call trace: | __kasan_unpoison_vmalloc+0xe4/0x478 | __vmalloc_node_range+0x77c/0x7b8 | __vmalloc_node+0x54/0x64 | init_IRQ+0x94/0xc8 | start_kernel+0x194/0x420 | __primary_switched+0xbc/0xc4 | Code: d34cfc08 aa1f03fa 8b081b39 d503201f (f9400328) | ---[ end trace 0000000000000000 ]--- | Kernel panic - not syncing: Attempted to kill the idle task! This is because init_vmalloc_pages() erroneously calls virt_to_page() on a vmalloc address, while virt_to_page() is only valid for addresses in the linear/direct map. Since init_vmalloc_pages() expects virtual addresses in the vmalloc range, it must use vmalloc_to_page() rather than virt_to_page(). We call init_vmalloc_pages() from __kasan_unpoison_vmalloc(), where we check !is_vmalloc_or_module_addr(), suggesting that we might encounter a non-vmalloc address. Luckily, this never happens. By design, we only call __kasan_unpoison_vmalloc() on pointers in the vmalloc area, and I have verified that we don't violate that expectation. Given that, is_vmalloc_or_module_addr() must always be true for any legitimate argument to __kasan_unpoison_vmalloc(). Correct init_vmalloc_pages() to use vmalloc_to_page(), and remove the redundant and misleading use of is_vmalloc_or_module_addr() in __kasan_unpoison_vmalloc(). Link: https://lkml.kernel.org/r/20230418164212.1775741-1-mark.rutland@arm.com Fixes: 6c2f761dad7851d8 ("kasan: fix zeroing vmalloc memory with HW_TAGS") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@google.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Marco Elver <elver@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.