From: "Darrick J. Wong" <djwong@kernel.org> mainline inclusion from mainline-v6.17-rc7 commit 3eefc0c2b78444b64feeb3783c017d6adc3cd3ce category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14828 CVE: CVE-2026-43158 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- xfs/592 and xfs/794 both trip this assertion in the leaf block freemap adjustment code after ~20 minutes of running on my test VMs: ASSERT(ichdr->firstused >= ichdr->count * sizeof(xfs_attr_leaf_entry_t) + xfs_attr3_leaf_hdr_size(leaf)); Upon enabling quite a lot more debugging code, I narrowed this down to fsstress trying to set a local extended attribute with namelen=3 and valuelen=71. This results in an entry size of 80 bytes. At the start of xfs_attr3_leaf_add_work, the freemap looks like this: i 0 base 448 size 0 rhs 448 count 46 i 1 base 388 size 132 rhs 448 count 46 i 2 base 2120 size 4 rhs 448 count 46 firstused = 520 where "rhs" is the first byte past the end of the leaf entry array. This is inconsistent -- the entries array ends at byte 448, but freemap[1] says there's free space starting at byte 388! By the end of the function, the freemap is in worse shape: i 0 base 456 size 0 rhs 456 count 47 i 1 base 388 size 52 rhs 456 count 47 i 2 base 2120 size 4 rhs 456 count 47 firstused = 440 Important note: 388 is not aligned with the entries array element size of 8 bytes. Based on the incorrect freemap, the name area starts at byte 440, which is below the end of the entries array! That's why the assertion triggers and the filesystem shuts down. How did we end up here? First, recall from the previous patch that the freemap array in an xattr leaf block is not intended to be a comprehensive map of all free space in the leaf block. In other words, it's perfectly legal to have a leaf block with: * 376 bytes in use by the entries array * freemap[0] has [base = 376, size = 8] * freemap[1] has [base = 388, size = 1500] * the space between 376 and 388 is free, but the freemap stopped tracking that some time ago If we add one xattr, the entries array grows to 384 bytes, and freemap[0] becomes [base = 384, size = 0]. So far, so good. But if we add a second xattr, the entries array grows to 392 bytes, and freemap[0] gets pushed up to [base = 392, size = 0]. This is bad, because freemap[1] hasn't been updated, and now the entries array and the free space claim the same space. The fix here is to adjust all freemap entries so that none of them collide with the entries array. Note that this fix relies on commit 2a2b5932db6758 ("xfs: fix attr leaf header freemap.size underflow") and the previous patch that resets zero length freemap entries to have base = 0. Cc: <stable@vger.kernel.org> # v2.6.12 Fixes: 1da177e4c3f415 ("Linux-2.6.12-rc2") Signed-off-by: "Darrick J. Wong" <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Conflicts: fs/xfs/libxfs/xfs_attr_leaf.c [Context conflicts] Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/xfs/libxfs/xfs_attr_leaf.c | 36 +++++++++++++++++++++++++++-------- 1 file changed, 28 insertions(+), 8 deletions(-) diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c index 10646ca83bc8..986c6f43b8ac 100644 --- a/fs/xfs/libxfs/xfs_attr_leaf.c +++ b/fs/xfs/libxfs/xfs_attr_leaf.c @@ -1406,6 +1406,7 @@ xfs_attr3_leaf_add_work( struct xfs_attr_leaf_name_local *name_loc; struct xfs_attr_leaf_name_remote *name_rmt; struct xfs_mount *mp; + int old_end, new_end; int tmp; int i; @@ -1496,17 +1497,36 @@ xfs_attr3_leaf_add_work( if (be16_to_cpu(entry->nameidx) < ichdr->firstused) ichdr->firstused = be16_to_cpu(entry->nameidx); - ASSERT(ichdr->firstused >= ichdr->count * sizeof(xfs_attr_leaf_entry_t) - + xfs_attr3_leaf_hdr_size(leaf)); - tmp = (ichdr->count - 1) * sizeof(xfs_attr_leaf_entry_t) - + xfs_attr3_leaf_hdr_size(leaf); + new_end = ichdr->count * sizeof(struct xfs_attr_leaf_entry) + + xfs_attr3_leaf_hdr_size(leaf); + old_end = new_end - sizeof(struct xfs_attr_leaf_entry); + + ASSERT(ichdr->firstused >= new_end); for (i = 0; i < XFS_ATTR_LEAF_MAPSIZE; i++) { - if (ichdr->freemap[i].base == tmp) { - ichdr->freemap[i].base += sizeof(xfs_attr_leaf_entry_t); + int diff = 0; + + if (ichdr->freemap[i].base == old_end) { + /* + * This freemap entry starts at the old end of the + * leaf entry array, so we need to adjust its base + * upward to accomodate the larger array. + */ + diff = sizeof(struct xfs_attr_leaf_entry); + } else if (ichdr->freemap[i].size > 0 && + ichdr->freemap[i].base < new_end) { + /* + * This freemap entry starts in the space claimed by + * the new leaf entry. Adjust its base upward to + * reflect that. + */ + diff = new_end - ichdr->freemap[i].base; + } + + if (diff) { + ichdr->freemap[i].base += diff; ichdr->freemap[i].size -= - min_t(uint16_t, ichdr->freemap[i].size, - sizeof(xfs_attr_leaf_entry_t)); + min_t(uint16_t, ichdr->freemap[i].size, diff); } /* -- 2.52.0