On 6/7/18 3:41 PM, Xu, Wen wrote: > Dear XFS developers, > > There is a NULL pointer dereference in xfs_trans_binval() when mounting and operating a crafted xfs image in 4.17-rc7 w/ for-next branch found by fuzzing. ... > - Reason > https://elixir.bootlin.com/linux/latest/source/fs/xfs/xfs_trans_buf.c#L610 > bp is NULL when calling xfs_trans_binval(). Yep, it looks like xfs_da_shrink_inode can error out before allocating bp (i.e. in this case with an out of bounds blkno). Does this fix it? ========= xfs: don't call xfs_da_shrink_inode with NULL bp xfs_attr3_leaf_create may have errored out before instantiating a buffer, for example if the blkno is out of range. In that case there is no work to do to remove it, and in fact xfs_da_shrink_inode will lead to an oops if we try. This also seems to fix a flaw where the original error from xfs_attr3_leaf_create gets overwritten in the cleanup case, and it removes a pointless assignment to bp which isn't used after this. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199969 Reported-by: Xu, Wen <wen.xu@xxxxxxxxxx> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> --- diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c index 2135b8e..397699d 100644 --- a/fs/xfs/libxfs/xfs_attr_leaf.c +++ b/fs/xfs/libxfs/xfs_attr_leaf.c @@ -803,9 +803,8 @@ STATIC void xfs_attr3_leaf_moveents(struct xfs_da_args *args, ASSERT(blkno == 0); error = xfs_attr3_leaf_create(args, blkno, &bp); if (error) { - error = xfs_da_shrink_inode(args, 0, bp); - bp = NULL; - if (error) + /* xfs_attr3_leaf_create may not have instantiated a block */ + if (bp && (xfs_da_shrink_inode(args, 0, bp) != 0)) goto out; xfs_idata_realloc(dp, size, XFS_ATTR_FORK); /* try to put */ memcpy(ifp->if_u1.if_data, tmpbuffer, size); /* it back */ -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
