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    SubjectRe: [PATCH AUTOSEL 3.18 6/6] ubifs: Check for name being NULL while mounting
    On Fri, Oct 05, 2018 at 06:24:42PM +0200, Richard Weinberger wrote:
    >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

    Hi Richard,

    I wasn't really looking at it from a security perspective. My thought
    process was that if a user (root or not) is doing action A, expecting
    result B but instead unexpectedly sees result C then it's a bug worth
    fixing in stable.

    If you think it's a risky change for stable I'd be happy to drop it.


    --
    Thanks,
    Sasha

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