From: Zhang Yi <yi.zhang@huawei.com> mainline inclusion from mainline-v6.19-rc4 commit 1bf6974822d1dba86cf11b5f05498581cf3488a2 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/15225 CVE: CVE-2026-45892 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- When allocating initialized blocks from a large unwritten extent, or when splitting an unwritten extent during end I/O and converting it to initialized, there is currently a potential issue of stale data if the extent needs to be split in the middle. 0 A B N [UUUUUUUUUUUU] U: unwritten extent [--DDDDDDDD--] D: valid data |<- ->| ----> this range needs to be initialized ext4_split_extent() first try to split this extent at B with EXT4_EXT_DATA_ENTIRE_VALID1 and EXT4_EXT_MAY_ZEROOUT flag set, but ext4_split_extent_at() failed to split this extent due to temporary lack of space. It zeroout B to N and mark the entire extent from 0 to N as written. 0 A B N [WWWWWWWWWWWW] W: written extent [SSDDDDDDDDZZ] Z: zeroed, S: stale data ext4_split_extent() then try to split this extent at A with EXT4_EXT_DATA_VALID2 flag set. This time, it split successfully and left a stale written extent from 0 to A. 0 A B N [WW|WWWWWWWWWW] [SS|DDDDDDDDZZ] Fix this by pass EXT4_EXT_DATA_PARTIAL_VALID1 to ext4_split_extent_at() when splitting at B, don't convert the entire extent to written and left it as unwritten after zeroing out B to N. The remaining work is just like the standard two-part split. ext4_split_extent() will pass the EXT4_EXT_DATA_VALID2 flag when it calls ext4_split_extent_at() for the second time, allowing it to properly handle the split. If the split is successful, it will keep extent from 0 to A as unwritten. Signed-off-by: Zhang Yi <yi.zhang@huawei.com> Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> Reviewed-by: Baokun Li <libaokun1@huawei.com> Cc: stable@kernel.org Message-ID: <20251129103247.686136-3-yi.zhang@huaweicloud.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Conflicts: fs/ext4/extents.c [Context conflicts] Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/ext4/extents.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 0f183a6232c0..c764ce4412fb 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3335,6 +3335,15 @@ static int ext4_split_extent_at(handle_t *handle, } if (!err) { + /* + * The first half contains partially valid data, the + * splitting of this extent has not been completed, fix + * extent length and ext4_split_extent() split will the + * first half again. + */ + if (split_flag & EXT4_EXT_DATA_PARTIAL_VALID1) + goto fix_extent_len; + /* update the extent length and mark as initialized */ ex->ee_len = cpu_to_le16(ee_len); ext4_ext_try_to_merge(handle, inode, path, ex); @@ -3407,7 +3416,9 @@ static int ext4_split_extent(handle_t *handle, split_flag1 |= EXT4_EXT_MARK_UNWRIT1 | EXT4_EXT_MARK_UNWRIT2; if (split_flag & EXT4_EXT_DATA_VALID2) - split_flag1 |= EXT4_EXT_DATA_ENTIRE_VALID1; + split_flag1 |= map->m_lblk > ee_block ? + EXT4_EXT_DATA_PARTIAL_VALID1 : + EXT4_EXT_DATA_ENTIRE_VALID1; err = ext4_split_extent_at(handle, inode, ppath, map->m_lblk + map->m_len, split_flag1, flags1); if (err) -- 2.52.0