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linux-next/kernel/bpf
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Tony Ambardar e23bb04b0c bpf: Fix sysfs export of empty BTF section 
If BTF data is missing or removed from the ELF section it is still exported
via sysfs as a zero-length file:

  root@OpenWrt:/# ls -l /sys/kernel/btf/vmlinux
  -r--r--r--    1 root    root    0 Jul 18 02:59 /sys/kernel/btf/vmlinux

Moreover, reads from this file succeed and leak kernel data:

  root@OpenWrt:/# hexdump -C /sys/kernel/btf/vmlinux|head -10
  000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
  *
  000cc0 00 00 00 00 00 00 00 00 00 00 00 00 80 83 b0 80 |................|
  000cd0 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
  000ce0 00 00 00 00 00 00 00 00 00 00 00 00 57 ac 6e 9d |............W.n.|
  000cf0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
  *
  002650 00 00 00 00 00 00 00 10 00 00 00 01 00 00 00 01 |................|
  002660 80 82 9a c4 80 85 97 80 81 a9 51 68 00 00 00 02 |..........Qh....|
  002670 80 25 44 dc 80 85 97 80 81 a9 50 24 81 ab c4 60 |.%D.......P$...`|

This situation was first observed with kernel 5.4.x, cross-compiled for a
MIPS target system. Fix by adding a sanity-check for export of zero-length
data sections.

Fixes: 341dfcf8d78e ("btf: expose BTF info through sysfs")
Signed-off-by: Tony Ambardar <Tony.Ambardar@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/b38db205a66238f70823039a8c531535864eaac5.1600417359.git.Tony.Ambardar@gmail.com
2020-09-21 21:50:24 +02:00
..
arraymap.c
bpf: Implement bpf iterator for array maps
2020-07-25 20:16:33 -07:00
bpf_iter.c
bpf: Fix a rcu_sched stall issue with bpf task/task_file iterator
2020-08-18 17:36:23 -07:00
bpf_lru_list.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206
2019-05-30 11:29:53 -07:00
bpf_lru_list.h
bpf: Fix a typo "inacitve" -> "inactive"
2020-04-06 21:54:10 +02:00
bpf_lsm.c
bpf: Use tracing helpers for lsm programs
2020-06-01 15:08:04 -07:00
bpf_struct_ops_types.h
bpf: tcp: Support tcp_congestion_ops in bpf
2020-01-09 08:46:18 -08:00
bpf_struct_ops.c
bpf: Set map_btf_{name, id} for all map types
2020-06-22 22:22:58 +02:00
btf.c
Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
2020-08-03 18:27:40 -07:00
cgroup.c
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
core.c
bpf: Delete repeated words in comments
2020-08-07 18:57:24 +02:00
cpumap.c
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00
devmap.c
Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
2020-07-04 17:48:34 -07:00
disasm.c
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 295
2019-06-05 17:36:38 +02:00
disasm.h
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 295
2019-06-05 17:36:38 +02:00
dispatcher.c
bpf: Remove bpf_image tree
2020-03-13 12:49:52 -07:00
hashtab.c
bpf: Do not use bucket_lock for hashmap iterator
2020-09-03 17:36:41 -07:00
helpers.c
bpf: Implement BPF ring buffer and verifier support for it
2020-06-01 14:38:22 -07:00
inode.c
bpf: Fix a rcu warning for bpffs map pretty-print
2020-09-15 18:17:39 -07:00
local_storage.c
bpf/local_storage: Fix build without CONFIG_CGROUP
2020-07-25 20:16:36 -07:00
lpm_trie.c
bpf: Remove redundant synchronize_rcu.
2020-07-01 08:07:13 -07:00
Makefile
bpf: Add bpf_prog iterator
2020-07-25 20:16:32 -07:00
map_in_map.c
bpf: Implement CAP_BPF
2020-05-15 17:29:41 +02:00
map_in_map.h
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206
2019-05-30 11:29:53 -07:00
map_iter.c
bpf: Change uapi for bpf iterator map elements
2020-08-06 16:39:14 -07:00
net_namespace.c
bpf: Add support for forced LINK_DETACH command
2020-08-01 20:38:28 -07:00
offload.c
bpf, offload: Replace bitwise AND by logical AND in bpf_prog_offload_info_fill
2020-02-17 16:53:49 +01:00
percpu_freelist.c
bpf: Dont iterate over possible CPUs with interrupts disabled
2020-02-24 16:18:20 -08:00
percpu_freelist.h
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206
2019-05-30 11:29:53 -07:00
prog_iter.c
bpf: Refactor bpf_iter_reg to have separate seq_info member
2020-07-25 20:16:32 -07:00
queue_stack_maps.c
bpf: Remove redundant synchronize_rcu.
2020-07-01 08:07:13 -07:00
reuseport_array.c
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
2020-07-11 00:46:00 -07:00
ringbuf.c
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
2020-07-11 00:46:00 -07:00
stackmap.c
bpf: Iterate through all PT_NOTE sections when looking for build id
2020-08-12 18:14:49 -07:00
syscall.c
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
2020-09-03 18:50:48 -07:00
sysfs_btf.c
bpf: Fix sysfs export of empty BTF section
2020-09-21 21:50:24 +02:00
task_iter.c
bpf: Avoid visit same object multiple times
2020-08-18 17:36:23 -07:00
tnum.c
bpf: Verifier, do explicit ALU32 bounds tracking
2020-03-30 14:59:53 -07:00
trampoline.c
bpf: lsm: Implement attach, detach and execution
2020-03-30 01:34:00 +02:00
verifier.c
treewide: Use fallthrough pseudo-keyword
2020-08-23 17:36:59 -05:00