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From: Vegard Nossum <>
To: syzbot <>
Cc:,,,, "David S. Miller" <>,,,,,,,, LKML <>,, Linux Netdev List <>,,,
Subject: Re: [syzbot] KASAN: vmalloc-out-of-bounds Read in __bpf_prog_put
Date: Mon, 24 Jan 2022 12:42:16 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, 20 Jan 2022 at 15:17, syzbot
<> wrote:
> syzbot suspects this issue was fixed by commit:
> commit 218d747a4142f281a256687bb513a135c905867b
> Author: John Fastabend <>
> Date:   Tue Jan 4 21:46:45 2022 +0000
>     bpf, sockmap: Fix double bpf_prog_put on error case in map_link

I can confirm the above commit fixes the issue, but it references a
slightly different report. Looks like the only difference is
__bpf_prog_put instead of bpf_prog_put:

KASAN: vmalloc-out-of-bounds Read in __bpf_prog_put
KASAN: vmalloc-out-of-bounds Read in bpf_prog_put

However, looking at the stack traces for the two bugs shows that
__bpf_prog_put() is really the location for both reports, see:
 kasan_report.cold+0x83/0xdf mm/kasan/report.c:450 mm/kasan/report.c:450
 __bpf_prog_put.constprop.0+0x1dd/0x220 kernel/bpf/syscall.c:1812
 bpf_prog_put kernel/bpf/syscall.c:1829 [inline]
 bpf_prog_put kernel/bpf/syscall.c:1829 [inline] kernel/bpf/syscall.c:1837

 kasan_report+0x19a/0x1f0 mm/kasan/report.c:450 mm/kasan/report.c:450
 __bpf_prog_put kernel/bpf/syscall.c:1812 [inline]
 __bpf_prog_put kernel/bpf/syscall.c:1812 [inline] kernel/bpf/syscall.c:1829
 bpf_prog_put+0x8c/0x4f0 kernel/bpf/syscall.c:1829 kernel/bpf/syscall.c:1829

Looks to me like the compiler's inlining decision caused syzbot to see
__bpf_prog_put() instead of bpf_prog_put(), but I can't tell if it's
because it got inlined or because of the .constprop.0 suffix... I
guess syzbot skips the [inline] entries when deciding which function
to report the bug in?

In any case:

#syz dup: KASAN: vmalloc-out-of-bounds Read in bpf_prog_put


  reply	other threads:[~2022-01-24 11:42 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-04 16:35 [syzbot] KASAN: vmalloc-out-of-bounds Read in __bpf_prog_put syzbot
2021-12-06 19:02 ` John Fastabend
2021-12-07 17:36 ` syzbot
2022-01-20 14:17 ` syzbot
2022-01-24 11:42   ` Vegard Nossum [this message]
2022-05-19 15:01     ` Dmitry Vyukov

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