On 10/18/20 11:40 PM, Chandan Babu R wrote:
XFS does not check for possible overflow of per-inode extent counter
fields when adding extents to either data or attr fork.
For e.g.
1. Insert 5 million xattrs (each having a value size of 255 bytes) and
then delete 50% of them in an alternating manner.
2. On a 4k block sized XFS filesystem instance, the above causes 98511
extents to be created in the attr fork of the inode.
xfsaild/loop0 2008 [003] 1475.127209: probe:xfs_inode_to_disk: (ffffffffa43fb6b0) if_nextents=98511 i_ino=131
3. The incore inode fork extent counter is a signed 32-bit
quantity. However the on-disk extent counter is an unsigned 16-bit
quantity and hence cannot hold 98511 extents.
4. The following incorrect value is stored in the attr extent counter,
# xfs_db -f -c 'inode 131' -c 'print core.naextents' /dev/loop0
core.naextents = -32561
This commit adds a new helper function (i.e.
xfs_iext_count_may_overflow()) to check for overflow of the per-inode
data and xattr extent counters. Future patches will use this function to
make sure that an FS operation won't cause the extent counter to
overflow.
Looks good to me
Reviewed-by: Allison Henderson <allison.henderson@xxxxxxxxxx>
Suggested-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Signed-off-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
---
fs/xfs/libxfs/xfs_inode_fork.c | 23 +++++++++++++++++++++++
fs/xfs/libxfs/xfs_inode_fork.h | 2 ++
2 files changed, 25 insertions(+)
diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
index 7575de5cecb1..8d48716547e5 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.c
+++ b/fs/xfs/libxfs/xfs_inode_fork.c
@@ -23,6 +23,7 @@
#include "xfs_da_btree.h"
#include "xfs_dir2_priv.h"
#include "xfs_attr_leaf.h"
+#include "xfs_types.h"
kmem_zone_t *xfs_ifork_zone;
@@ -728,3 +729,25 @@ xfs_ifork_verify_local_attr(
return 0;
}
+
+int
+xfs_iext_count_may_overflow(
+ struct xfs_inode *ip,
+ int whichfork,
+ int nr_to_add)
+{
+ struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);
+ uint64_t max_exts;
+ uint64_t nr_exts;
+
+ if (whichfork == XFS_COW_FORK)
+ return 0;
+
+ max_exts = (whichfork == XFS_ATTR_FORK) ? MAXAEXTNUM : MAXEXTNUM;
+
+ nr_exts = ifp->if_nextents + nr_to_add;
+ if (nr_exts < ifp->if_nextents || nr_exts > max_exts)
+ return -EFBIG;
+
+ return 0;
+}
diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index a4953e95c4f3..0beb8e2a00be 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -172,5 +172,7 @@ extern void xfs_ifork_init_cow(struct xfs_inode *ip);
int xfs_ifork_verify_local_data(struct xfs_inode *ip);
int xfs_ifork_verify_local_attr(struct xfs_inode *ip);
+int xfs_iext_count_may_overflow(struct xfs_inode *ip, int whichfork,
+ int nr_to_add);
#endif /* __XFS_INODE_FORK_H__ */
