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Message-ID: <f74665d1-4d28-01a2-5694-b06fde202d39@ghiti.fr>
Date: Thu, 28 Sep 2023 10:15:56 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Edward AD <twuufnxlz@...il.com>, conor@...nel.org
Cc: syzbot+8d2757d62d403b2d9275@...kaller.appspotmail.com,
gregkh@...uxfoundation.org, jirislaby@...nel.org,
linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
syzkaller-bugs@...glegroups.com, paul.walmsley@...ive.com,
palmer@...belt.com, aou@...s.berkeley.edu, guoren@...nel.org,
alexghiti@...osinc.com, liushixin2@...wei.com,
linux-riscv@...ts.infradead.org
Subject: Re: [PATCH] riscv: fix out of bounds in walk_stackframe
Oh and BTW, any idea why linux-riscv was not in CC for the initial report?
On 28/09/2023 10:02, Alexandre Ghiti wrote:
> Hi Edward,
>
> On 26/09/2023 13:43, Edward AD wrote:
>> Increase the check on the frame after assigning its value. This is to
>> prevent
>> frame access from crossing boundaries.
>>
>> Closes:
>> https://lore.kernel.org/all/20230926105949.1025995-2-twuufnxlz@gmail.com/
>> Fixes: 5d8544e2d007 ("RISC-V: Generic library routines and assembly")
>> Reported-and-tested-by:
>> syzbot+8d2757d62d403b2d9275@...kaller.appspotmail.com
>> Link:
>> https://lore.kernel.org/all/0000000000000170df0605ccf91a@google.com/T/
>> Signed-off-by: Edward AD <twuufnxlz@...il.com>
>> ---
>> arch/riscv/kernel/stacktrace.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/riscv/kernel/stacktrace.c
>> b/arch/riscv/kernel/stacktrace.c
>> index 64a9c093aef9..53bd18672329 100644
>> --- a/arch/riscv/kernel/stacktrace.c
>> +++ b/arch/riscv/kernel/stacktrace.c
>> @@ -54,6 +54,8 @@ void notrace walk_stackframe(struct task_struct
>> *task, struct pt_regs *regs,
>> break;
>> /* Unwind stack frame */
>> frame = (struct stackframe *)fp - 1;
>> + if (!virt_addr_valid(frame))
>> + break;
>> sp = fp;
>> if (regs && (regs->epc == pc) && (frame->fp & 0x7)) {
>> fp = frame->ra;
>
>
> virt_addr_valid() works on kernel linear addresses, not on vmalloc
> addresses, which is the case here (0xff20000006d37c38 belongs to the
> vmalloc region: see
> https://elixir.bootlin.com/linux/latest/source/Documentation/riscv/vm-layout.rst#L125).
> So this fix can't work.
>
> I'm a bit surprised though of this out-of-bounds access since
> CONFIG_FRAME_POINTER is enabled, so there may be a real issue here
> (the console output is horrible, lots of backtraces, which is weird),
> so it may be worth digging into that.
>
> Thanks,
>
> Alex
>
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
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