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    Subject[PATCH 5.8 557/633] ntfs: add check for mft record size in superblock
    Date
    From: Rustam Kovhaev <rkovhaev@gmail.com>

    [ Upstream commit 4f8c94022f0bc3babd0a124c0a7dcdd7547bd94e ]

    Number of bytes allocated for mft record should be equal to the mft record
    size stored in ntfs superblock as reported by syzbot, userspace might
    trigger out-of-bounds read by dereferencing ctx->attr in ntfs_attr_find()

    Reported-by: syzbot+aed06913f36eff9b544e@syzkaller.appspotmail.com
    Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Tested-by: syzbot+aed06913f36eff9b544e@syzkaller.appspotmail.com
    Acked-by: Anton Altaparmakov <anton@tuxera.com>
    Link: https://syzkaller.appspot.com/bug?extid=aed06913f36eff9b544e
    Link: https://lkml.kernel.org/r/20200824022804.226242-1-rkovhaev@gmail.com
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/ntfs/inode.c | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
    index d4359a1df3d5e..84933a0af49b6 100644
    --- a/fs/ntfs/inode.c
    +++ b/fs/ntfs/inode.c
    @@ -1809,6 +1809,12 @@ int ntfs_read_inode_mount(struct inode *vi)
    brelse(bh);
    }

    + if (le32_to_cpu(m->bytes_allocated) != vol->mft_record_size) {
    + ntfs_error(sb, "Incorrect mft record size %u in superblock, should be %u.",
    + le32_to_cpu(m->bytes_allocated), vol->mft_record_size);
    + goto err_out;
    + }
    +
    /* Apply the mst fixups. */
    if (post_read_mst_fixup((NTFS_RECORD*)m, vol->mft_record_size)) {
    /* FIXME: Try to use the $MFTMirr now. */
    --
    2.25.1


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