From: Greg KH <gregkh@linuxfoundation.org>
To: Kurt Manucredo <fuzzybritches0@gmail.com>
Cc: linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [PATCH] bpf: core: fix shift-out-of-bounds in ___bpf_prog_run
Date: Thu, 27 May 2021 06:29:39 +0200 [thread overview]
Message-ID: <YK8gM6LoV8q8AkhE@kroah.com> (raw)
In-Reply-To: <60aec085.1c69fb81.972cc.0bfb@mx.google.com>
On Wed, May 26, 2021 at 11:40:27PM +0200, Kurt Manucredo wrote:
> Fix shift-out-of-bounds in ___bpf_prog_run().
>
> UBSAN: shift-out-of-bounds in kernel/bpf/core.c:1414:2
> shift exponent 248 is too large for 32-bit type 'unsigned int'
> https://syzkaller.appspot.com/bug?id=edb51be4c9a320186328893287bb30d5eed09231
>
> Reported-by: syzbot+bed360704c521841c85d@syzkaller.appspotmail.com
> Signed-off-by: Kurt Manucredo <fuzzybritches0@gmail.com>
> ---
> kernel/bpf/core.c | 31 +++++++++++++++++++++++++++++--
> 1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 5e31ee9f7512..35cba247c531 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -1411,11 +1411,38 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
> ALU(SUB, -)
> ALU(AND, &)
> ALU(OR, |)
> - ALU(LSH, <<)
> - ALU(RSH, >>)
> ALU(XOR, ^)
> ALU(MUL, *)
> #undef ALU
> +#define ALU(OPCODE, OP) \
> + ALU64_##OPCODE##_X: \
> + if (SRC >= 64) \
> + DST = 0; \
> + else \
> + DST = DST OP SRC; \
> + CONT; \
> + ALU_##OPCODE##_X: \
> + if (SRC >= 32) \
> + DST = 0; \
> + else \
> + DST = (u32) DST OP (u32) SRC; \
> + CONT; \
> + ALU64_##OPCODE##_K: \
> + if (IMM >= 64) \
> + DST = 0; \
> + else \
> + DST = DST OP IMM; \
> + CONT; \
> + ALU_##OPCODE##_K: \
> + if (IMM >= 32) \
> + DST = 0; \
> + else \
> + DST = (u32) DST OP (u32) IMM; \
> + CONT;
> +
> + ALU(LSH, <<)
> + ALU(RSH, >>)
> +#undef ALU
> ALU_NEG:
> DST = (u32) -DST;
> CONT;
> --
> 2.30.2
>
This looks odd, shouldn't the caller be checked before it gets to this
part of the code?
did syzbot pass its tests with this change?
thanks,
greg k-h
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next prev parent reply other threads:[~2021-05-27 4:29 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-26 21:40 [PATCH] bpf: core: fix shift-out-of-bounds in ___bpf_prog_run Kurt Manucredo
2021-05-27 4:29 ` Greg KH [this message]
2021-06-01 14:33 ` [PATCH v2] " Kurt Manucredo
2021-06-01 15:43 ` Greg KH
2021-06-01 21:28 ` Kurt Manucredo
2021-06-02 6:09 ` Greg KH
2021-06-02 6:36 ` Pavel Skripkin
2021-06-04 21:15 ` Kurt Manucredo
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