On Sat, Nov 14, 2020 at 11:32:49AM +0100, Christoph Hellwig wrote: > On Fri, Nov 13, 2020 at 09:50:44AM +0800, Gao Xiang wrote: > > Currently, commit e9e2eae89ddb dropped a (int) decoration from > > XFS_LITINO(mp), and since sizeof() expression is also involved, > > the result of XFS_LITINO(mp) is simply as the size_t type > > (commonly unsigned long). > > > > Considering the expression in xfs_attr_shortform_bytesfit(): > > offset = (XFS_LITINO(mp) - bytes) >> 3; > > let "bytes" be (int)340, and > > "XFS_LITINO(mp)" be (unsigned long)336. > > > > on 64-bit platform, the expression is > > offset = ((unsigned long)336 - (int)340) >> 3 = > > (int)(0xfffffffffffffffcUL >> 3) = -1 > > > > but on 32-bit platform, the expression is > > offset = ((unsigned long)336 - (int)340) >> 3 = > > (int)(0xfffffffcUL >> 3) = 0x1fffffff > > instead. > > > > so offset becomes a large positive number on 32-bit platform, and > > cause xfs_attr_shortform_bytesfit() returns maxforkoff rather than 0. > > > > Therefore, one result is > > "ASSERT(new_size <= XFS_IFORK_SIZE(ip, whichfork));" > > > > assertion failure in xfs_idata_realloc(), which was also the root > > cause of the original bugreport from Dennis, see: > > https://bugzilla.redhat.com/show_bug.cgi?id=1894177 > > > > And it can also be manually triggered with the following commands: > > $ touch a; > > $ setfattr -n user.0 -v "`seq 0 80`" a; > > $ setfattr -n user.1 -v "`seq 0 80`" a > > > > on 32-bit platform. > > > > Fix the case in xfs_attr_shortform_bytesfit() by bailing out > > "XFS_LITINO(mp) < bytes" in advance suggested by Eric and a misleading > > comment together with this bugfix suggested by Darrick. It seems the > > other users of XFS_LITINO(mp) are not impacted. > > > > Reported-by: Dennis Gilmore <dgilmore@xxxxxxxxxx> > > Fixes: e9e2eae89ddb ("xfs: only check the superblock version for dinode size calculation") > > Cc: <stable@xxxxxxxxxxxxxxx> # 5.7+ > > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx> > > --- > > changes since v1: > > - fix 2 typos ">> 8" to ">> 3" mentioned by Eric; > > - directly bail out "XFS_LITINO(mp) < bytes" suggested > > by Eric and Darrick; > > - fix a misleading comment together suggested by Darrick; > > - since (int) decorator doesn't need to be added, so update > > the patch subject as well. > > > > fs/xfs/libxfs/xfs_attr_leaf.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c > > index bb128db220ac..c8d91034850b 100644 > > --- a/fs/xfs/libxfs/xfs_attr_leaf.c > > +++ b/fs/xfs/libxfs/xfs_attr_leaf.c > > @@ -515,7 +515,7 @@ xfs_attr_copy_value( > > *========================================================================*/ > > > > /* > > - * Query whether the requested number of additional bytes of extended > > + * Query whether the total requested number of attr fork bytes of extended > > * attribute space will be able to fit inline. > > * > > * Returns zero if not, else the di_forkoff fork offset to be used in the > > @@ -535,6 +535,10 @@ xfs_attr_shortform_bytesfit( > > int maxforkoff; > > int offset; > > > > + /* there is no chance we can fit */ > > Maybe: > > /* > * Check if the new size could fit at all first: > */ ok, let me quick revise it as the next version. > > Otherwise looks good: > > Reviewed-by: Christoph Hellwig <hch@xxxxxx> Thanks! Thanks, Gao Xiang >
