On Mon, 23 Jun 2025, Milan Broz wrote:
> On 6/23/25 1:11 PM, Herbert Xu wrote:
> > On Mon, Jun 23, 2025 at 11:40:39AM +0200, Mikulas Patocka wrote:
> > >
> > > 345 bytes on the stack - I think it's too much, given the fact that it
> > > already uses 345 bytes (from SHASH_DESC_ON_STACK) and it may be called in
> > > a tasklet context. I'd prefer a solution that allocates less bytes.
> > >
> > > I don't see the beginning of this thread, so I'd like to ask what's the
> > > problem here, what algorithm other than md5 is used here that causes the
> > > buffer overflow?
> >
> > The md5 export size has increased due to the partial block API
> > thus triggering the overflow.
> >
> > How about this patch?
OK. I accepted the patch and committed it to the linux-dm git.
Mikulas
> For v2:
>
> Tested-by: Milan Broz <gmazyl...@gmail.com>
>
> Just for the context, the patch fixes OOPS on 32bit (but 64bit should overflow
> struct too):
>
> : Oops: Oops: 0000 [#1] SMP
> : CPU: 1 UID: 0 PID: 12 Comm: kworker/u16:0 Not tainted 6.16.0-rc2+ #993
> PREEMPT(full)
> : Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference
> Platform, BIOS 6.00 11/12/2020
> : Workqueue: kcryptd-254:0-1 kcryptd_crypt [dm_crypt]
> : EIP: __crypto_shash_export+0xf/0x90
> : Code: 4a c1 c7 40 20 a0 b4 4a c1 81 cf 0e 00 04 08 89 78 50 e9 2b ff ff ff
> 8d 74 26 00 55 89 e5 57 56 53 89 c3 89 d6 8b 00 8b 40 14 <8b> 50 fc f6 40 13
> 01 74 04 4a 2b 50 14 85 c9 74 10 89 f2 89 d8 ff
> : EAX: 303a3435 EBX: c3007c90 ECX: 00000000 EDX: c3007c38
> : ESI: c3007c38 EDI: c3007c90 EBP: c3007bfc ESP: c3007bf0
> : DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010216
> : CR0: 80050033 CR2: 303a3431 CR3: 04fbe000 CR4: 00350e90
> : Call Trace:
> : crypto_shash_export+0x65/0xc0
> : crypt_iv_lmk_one+0x106/0x1a0 [dm_crypt]
>
> ...
>
> The bisect was
>
> efd62c85525e212705368b24eb90ef10778190f5 is the first bad commit
> commit efd62c85525e212705368b24eb90ef10778190f5 (HEAD)
> Author: Herbert Xu <herb...@gondor.apana.org.au>
> Date: Fri Apr 18 10:59:04 2025 +0800
>
> crypto: md5-generic - Use API partial block handling
>
> Use the Crypto API partial block handling.
>
> Milan
>
