* [PATCH bpf-next] bpf: Mark bpf prog stack with kmsan_unposion_memory in interpreter mode
@ 2024-03-28 18:58 Martin KaFai Lau
2024-03-29 2:10 ` patchwork-bot+netdevbpf
0 siblings, 1 reply; 2+ messages in thread
From: Martin KaFai Lau @ 2024-03-28 18:58 UTC (permalink / raw)
To: bpf
Cc: Alexei Starovoitov, Andrii Nakryiko, Daniel Borkmann,
kernel-team, syzbot+603bcd9b0bf1d94dbb9b,
syzbot+eb02dc7f03dce0ef39f3, syzbot+b4e65ca24fd4d0c734c3,
syzbot+d2b113dc9fea5e1d2848, syzbot+1a3cf6f08d68868f9db3,
Yonghong Song
From: Martin KaFai Lau <martin.lau@kernel.org>
syzbot reported uninit memory usages during map_{lookup,delete}_elem.
==========
BUG: KMSAN: uninit-value in __dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline]
BUG: KMSAN: uninit-value in dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796
__dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline]
dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796
____bpf_map_lookup_elem kernel/bpf/helpers.c:42 [inline]
bpf_map_lookup_elem+0x5c/0x80 kernel/bpf/helpers.c:38
___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
__bpf_prog_run256+0xb5/0xe0 kernel/bpf/core.c:2237
==========
The reproducer should be in the interpreter mode.
The C reproducer is trying to run the following bpf prog:
0: (18) r0 = 0x0
2: (18) r1 = map[id:49]
4: (b7) r8 = 16777216
5: (7b) *(u64 *)(r10 -8) = r8
6: (bf) r2 = r10
7: (07) r2 += -229
^^^^^^^^^^
8: (b7) r3 = 8
9: (b7) r4 = 0
10: (85) call dev_map_lookup_elem#1543472
11: (95) exit
It is due to the "void *key" (r2) passed to the helper. bpf allows uninit
stack memory access for bpf prog with the right privileges. This patch
uses kmsan_unpoison_memory() to mark the stack as initialized.
This should address different syzbot reports on the uninit "void *key"
argument during map_{lookup,delete}_elem.
Reported-by: syzbot+603bcd9b0bf1d94dbb9b@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/000000000000f9ce6d061494e694@google.com/
Reported-by: syzbot+eb02dc7f03dce0ef39f3@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/000000000000a5c69c06147c2238@google.com/
Reported-by: syzbot+b4e65ca24fd4d0c734c3@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/000000000000ac56fb06143b6cfa@google.com/
Reported-by: syzbot+d2b113dc9fea5e1d2848@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/0000000000000d69b206142d1ff7@google.com/
Reported-by: syzbot+1a3cf6f08d68868f9db3@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/bpf/0000000000006f876b061478e878@google.com/
Tested-by: syzbot+1a3cf6f08d68868f9db3@syzkaller.appspotmail.com
Suggested-by: Yonghong Song <yonghong.song@linux.dev>
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---
kernel/bpf/core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 5aacb1d3c4cc..ab400cdd7d7a 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2218,6 +2218,7 @@ static unsigned int PROG_NAME(stack_size)(const void *ctx, const struct bpf_insn
u64 stack[stack_size / sizeof(u64)]; \
u64 regs[MAX_BPF_EXT_REG] = {}; \
\
+ kmsan_unpoison_memory(stack, sizeof(stack)); \
FP = (u64) (unsigned long) &stack[ARRAY_SIZE(stack)]; \
ARG1 = (u64) (unsigned long) ctx; \
return ___bpf_prog_run(regs, insn); \
@@ -2231,6 +2232,7 @@ static u64 PROG_NAME_ARGS(stack_size)(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5, \
u64 stack[stack_size / sizeof(u64)]; \
u64 regs[MAX_BPF_EXT_REG]; \
\
+ kmsan_unpoison_memory(stack, sizeof(stack)); \
FP = (u64) (unsigned long) &stack[ARRAY_SIZE(stack)]; \
BPF_R1 = r1; \
BPF_R2 = r2; \
--
2.43.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH bpf-next] bpf: Mark bpf prog stack with kmsan_unposion_memory in interpreter mode
2024-03-28 18:58 [PATCH bpf-next] bpf: Mark bpf prog stack with kmsan_unposion_memory in interpreter mode Martin KaFai Lau
@ 2024-03-29 2:10 ` patchwork-bot+netdevbpf
0 siblings, 0 replies; 2+ messages in thread
From: patchwork-bot+netdevbpf @ 2024-03-29 2:10 UTC (permalink / raw)
To: Martin KaFai Lau
Cc: bpf, ast, andrii, daniel, kernel-team,
syzbot+603bcd9b0bf1d94dbb9b, syzbot+eb02dc7f03dce0ef39f3,
syzbot+b4e65ca24fd4d0c734c3, syzbot+d2b113dc9fea5e1d2848,
syzbot+1a3cf6f08d68868f9db3, yonghong.song
Hello:
This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:
On Thu, 28 Mar 2024 11:58:01 -0700 you wrote:
> From: Martin KaFai Lau <martin.lau@kernel.org>
>
> syzbot reported uninit memory usages during map_{lookup,delete}_elem.
>
> ==========
> BUG: KMSAN: uninit-value in __dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline]
> BUG: KMSAN: uninit-value in dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796
> __dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline]
> dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796
> ____bpf_map_lookup_elem kernel/bpf/helpers.c:42 [inline]
> bpf_map_lookup_elem+0x5c/0x80 kernel/bpf/helpers.c:38
> ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
> __bpf_prog_run256+0xb5/0xe0 kernel/bpf/core.c:2237
> ==========
>
> [...]
Here is the summary with links:
- [bpf-next] bpf: Mark bpf prog stack with kmsan_unposion_memory in interpreter mode
https://git.kernel.org/bpf/bpf-next/c/e8742081db7d
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
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2024-03-28 18:58 [PATCH bpf-next] bpf: Mark bpf prog stack with kmsan_unposion_memory in interpreter mode Martin KaFai Lau
2024-03-29 2:10 ` patchwork-bot+netdevbpf
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