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SubjectRe: [PATCH AUTOSEL 3.18 6/6] ubifs: Check for name being NULL while mounting
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Sasha,

Am Freitag, 5. Oktober 2018, 18:17:50 CEST schrieb Sasha Levin:
> From: Richard Weinberger <richard@nod.at>
>
> [ Upstream commit 37f31b6ca4311b94d985fb398a72e5399ad57925 ]
>
> The requested device name can be NULL or an empty string.
> Check for that and refuse to continue. UBIFS has to do this manually
> since we cannot use mount_bdev(), which checks for this condition.
>
> Fixes: 1e51764a3c2ac ("UBIFS: add new flash file system")
> Reported-by: syzbot+38bd0f7865e5c6379280@syzkaller.appspotmail.com
> Signed-off-by: Richard Weinberger <richard@nod.at>
> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>

I'm not sure whether it makes sense to apply this patch to stable.
1. You need to be the real root to hit this code path.
2. Access is read-only, for an attacker it is useless.

If we look at the code:
if (name[0] != 'u' || name[1] != 'b' || name[2] != 'i')
return ERR_PTR(-EINVAL);

/* ubi:NAME method */
if ((name[3] == ':' || name[3] == '!') && name[4] != '\0')

name can be NULL, so we access just a few bytes.

Thanks,
//richard


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