Re: [PATCH] FS, NET: Fix KMSAN uninit-value in vfs_write

[Marc Kleine-Budde]

On 14.03.2023 16:04:45, Ivan Orlov wrote:
> Syzkaller reported the following issue:
> 
> =====================================================
> BUG: KMSAN: uninit-value in aio_rw_done fs/aio.c:1520 [inline]
> BUG: KMSAN: uninit-value in aio_write+0x899/0x950 fs/aio.c:1600
>  aio_rw_done fs/aio.c:1520 [inline]
>  aio_write+0x899/0x950 fs/aio.c:1600
>  io_submit_one+0x1d1c/0x3bf0 fs/aio.c:2019
>  __do_sys_io_submit fs/aio.c:2078 [inline]
>  __se_sys_io_submit+0x293/0x770 fs/aio.c:2048
>  __x64_sys_io_submit+0x92/0xd0 fs/aio.c:2048
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Uninit was created at:
>  slab_post_alloc_hook mm/slab.h:766 [inline]
>  slab_alloc_node mm/slub.c:3452 [inline]
>  __kmem_cache_alloc_node+0x71f/0xce0 mm/slub.c:3491
>  __do_kmalloc_node mm/slab_common.c:967 [inline]
>  __kmalloc+0x11d/0x3b0 mm/slab_common.c:981
>  kmalloc_array include/linux/slab.h:636 [inline]
>  bcm_tx_setup+0x80e/0x29d0 net/can/bcm.c:930
>  bcm_sendmsg+0x3a2/0xce0 net/can/bcm.c:1351
>  sock_sendmsg_nosec net/socket.c:714 [inline]
>  sock_sendmsg net/socket.c:734 [inline]
>  sock_write_iter+0x495/0x5e0 net/socket.c:1108
>  call_write_iter include/linux/fs.h:2189 [inline]
>  aio_write+0x63a/0x950 fs/aio.c:1600
>  io_submit_one+0x1d1c/0x3bf0 fs/aio.c:2019
>  __do_sys_io_submit fs/aio.c:2078 [inline]
>  __se_sys_io_submit+0x293/0x770 fs/aio.c:2048
>  __x64_sys_io_submit+0x92/0xd0 fs/aio.c:2048
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> CPU: 1 PID: 5034 Comm: syz-executor350 Not tainted 6.2.0-rc6-syzkaller-80422-geda666ff2276 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/12/2023
> =====================================================
> 
> We can follow the call chain and find that 'bcm_tx_setup' function calls 'memcpy_from_msg'
> to copy some content to the newly allocated frame of 'op->frames'. After that the 'len'
> field of copied structure being compared with some constant value (64 or 8). However, if
> 'memcpy_from_msg' returns an error, we will compare some uninitialized memory. This triggers
> 'uninit-value' issue.
> 
> This patch will add 'memcpy_from_msg' possible errors processing to avoid uninit-value
> issue.
> 
> Tested via syzkaller
> 
> Reported-by: syzbot+c9bfd85eca611ebf5db1@xxxxxxxxxxxxxxxxxxxxxxxxx
> Link: https://syzkaller.appspot.com/bug?id=47f897f8ad958bbde5790ebf389b5e7e0a345089
> Signed-off-by: Ivan Orlov <ivan.orlov0322@xxxxxxxxx>

Applied to linux-can.

Thanks,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
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