]> git.baikalelectronics.ru Git - kernel.git/commit
bpf: Add preempt_count_{sub,add} into btf id deny list
authorYafang <laoar.shao@gmail.com>
Thu, 13 Apr 2023 02:52:48 +0000 (02:52 +0000)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 24 May 2023 16:32:38 +0000 (17:32 +0100)
commitf949c430e3ba9a91e964f7858570cec57d1a5c54
tree3f0000c30feb74d4e114d5a891459aee19d87b0f
parentc6fa5e60614aab091ab64027a193b54a6bbacf7c
bpf: Add preempt_count_{sub,add} into btf id deny list

[ Upstream commit c11bd046485d7bf1ca200db0e7d0bdc4bafdd395 ]

The recursion check in __bpf_prog_enter* and __bpf_prog_exit*
leave preempt_count_{sub,add} unprotected. When attaching trampoline to
them we get panic as follows,

[  867.843050] BUG: TASK stack guard page was hit at 0000000009d325cf (stack is 0000000046a46a15..00000000537e7b28)
[  867.843064] stack guard page: 0000 [#1] PREEMPT SMP NOPTI
[  867.843067] CPU: 8 PID: 11009 Comm: trace Kdump: loaded Not tainted 6.2.0+ #4
[  867.843100] Call Trace:
[  867.843101]  <TASK>
[  867.843104]  asm_exc_int3+0x3a/0x40
[  867.843108] RIP: 0010:preempt_count_sub+0x1/0xa0
[  867.843135]  __bpf_prog_enter_recur+0x17/0x90
[  867.843148]  bpf_trampoline_6442468108_0+0x2e/0x1000
[  867.843154]  ? preempt_count_sub+0x1/0xa0
[  867.843157]  preempt_count_sub+0x5/0xa0
[  867.843159]  ? migrate_enable+0xac/0xf0
[  867.843164]  __bpf_prog_exit_recur+0x2d/0x40
[  867.843168]  bpf_trampoline_6442468108_0+0x55/0x1000
...
[  867.843788]  preempt_count_sub+0x5/0xa0
[  867.843793]  ? migrate_enable+0xac/0xf0
[  867.843829]  __bpf_prog_exit_recur+0x2d/0x40
[  867.843837] BUG: IRQ stack guard page was hit at 0000000099bd8228 (stack is 00000000b23e2bc4..000000006d95af35)
[  867.843841] BUG: IRQ stack guard page was hit at 000000005ae07924 (stack is 00000000ffd69623..0000000014eb594c)
[  867.843843] BUG: IRQ stack guard page was hit at 00000000028320f0 (stack is 00000000034b6438..0000000078d1bcec)
[  867.843842]  bpf_trampoline_6442468108_0+0x55/0x1000
...

That is because in __bpf_prog_exit_recur, the preempt_count_{sub,add} are
called after prog->active is decreased.

Fixing this by adding these two functions into btf ids deny list.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Yafang <laoar.shao@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Acked-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/r/20230413025248.79764-1-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
kernel/bpf/verifier.c