[PATCH OLK-6.6 0/3] Fix CVE-2026-45892
Fix CVE-2026-45892 Zhang Yi (3): ext4: subdivide EXT4_EXT_DATA_VALID1 ext4: don't zero the entire extent if EXT4_EXT_DATA_PARTIAL_VALID1 ext4: drop extent cache after doing PARTIAL_VALID1 zeroout fs/ext4/extents.c | 37 +++++++++++++++++++++++++++++++------ 1 file changed, 31 insertions(+), 6 deletions(-) -- 2.52.0
From: Zhang Yi <yi.zhang@huawei.com> mainline inclusion from mainline-v6.19-rc4 commit 22784ca541c0f01c5ebad14e8228298dc0a390ed 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 splitting an extent, if the EXT4_GET_BLOCKS_CONVERT flag is set and it is necessary to split the target extent in the middle, ext4_split_extent() first handles splitting the latter half of the extent and passes the EXT4_EXT_DATA_VALID1 flag. This flag implies that all blocks before the split point contain valid data; however, this assumption is incorrect. Therefore, subdivid EXT4_EXT_DATA_VALID1 into EXT4_EXT_DATA_ENTIRE_VALID1 and EXT4_EXT_DATA_PARTIAL_VALID1, which indicate that the first half of the extent is either entirely valid or only partially valid, respectively. These two flags cannot be set simultaneously. This patch does not use EXT4_EXT_DATA_PARTIAL_VALID1, it only replaces EXT4_EXT_DATA_VALID1 with EXT4_EXT_DATA_ENTIRE_VALID1 at the location where it is set, no logical changes. 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: <20251129103247.686136-2-yi.zhang@huaweicloud.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Conflicts: fs/ext4/extents.c [Context conflicts] Signed-off-by: Yang Erkun <yangerkun@huawei.com> Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/ext4/extents.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 24a09d2caea5..4a865abf839c 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -43,8 +43,13 @@ #define EXT4_EXT_MARK_UNWRIT1 0x2 /* mark first half unwritten */ #define EXT4_EXT_MARK_UNWRIT2 0x4 /* mark second half unwritten */ -#define EXT4_EXT_DATA_VALID1 0x8 /* first half contains valid data */ -#define EXT4_EXT_DATA_VALID2 0x10 /* second half contains valid data */ +/* first half contains valid data */ +#define EXT4_EXT_DATA_ENTIRE_VALID1 0x8 /* has entirely valid data */ +#define EXT4_EXT_DATA_PARTIAL_VALID1 0x10 /* has partially valid data */ +#define EXT4_EXT_DATA_VALID1 (EXT4_EXT_DATA_ENTIRE_VALID1 | \ + EXT4_EXT_DATA_PARTIAL_VALID1) + +#define EXT4_EXT_DATA_VALID2 0x20 /* second half contains valid data */ static __le32 ext4_extent_block_csum(struct inode *inode, struct ext4_extent_header *eh) @@ -3212,8 +3217,9 @@ static int ext4_split_extent_at(handle_t *handle, unsigned int ee_len, depth; int err = 0; - BUG_ON((split_flag & (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2)) == - (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2)); + BUG_ON((split_flag & EXT4_EXT_DATA_VALID1) == EXT4_EXT_DATA_VALID1); + BUG_ON((split_flag & EXT4_EXT_DATA_VALID1) && + (split_flag & EXT4_EXT_DATA_VALID2)); /* Do not cache extents that are in the process of being modified. */ flags |= EXT4_EX_NOCACHE; @@ -3400,7 +3406,7 @@ 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_VALID1; + split_flag1 |= EXT4_EXT_DATA_ENTIRE_VALID1; err = ext4_split_extent_at(handle, inode, ppath, map->m_lblk + map->m_len, split_flag1, flags1); if (err) @@ -3755,7 +3761,7 @@ static int ext4_split_convert_extents(handle_t *handle, /* Convert to unwritten */ if (flags & EXT4_GET_BLOCKS_CONVERT_UNWRITTEN) { - split_flag |= EXT4_EXT_DATA_VALID1; + split_flag |= EXT4_EXT_DATA_ENTIRE_VALID1; /* Split the existing unwritten extent */ } else if (flags & (EXT4_GET_BLOCKS_UNWRIT_EXT | EXT4_GET_BLOCKS_CONVERT)) { -- 2.52.0
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: Yang Erkun <yangerkun@huawei.com> 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 4a865abf839c..9476c1c7e9be 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3334,6 +3334,15 @@ 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); @@ -3406,7 +3415,9 @@ 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
From: Zhang Yi <yi.zhang@huawei.com> mainline inclusion from mainline-v6.19-rc4 commit 6d882ea3b0931b43530d44149b79fcd4ffc13030 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 splitting an unwritten extent in the middle and converting it to initialized in ext4_split_extent() with the EXT4_EXT_MAY_ZEROOUT and EXT4_EXT_DATA_VALID2 flags set, it could leave a stale unwritten extent. Assume we have an unwritten file and buffered write in the middle of it without dioread_nolock enabled, it will allocate blocks as written extent. 0 A B N [UUUUUUUUUUUU] on-disk extent U: unwritten extent [UUUUUUUUUUUU] extent status tree [--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_PARTIAL_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 leave the entire extent as unwritten. 0 A B N [UUUUUUUUUUUU] on-disk extent [UUUUUUUUUUUU] extent status tree [--DDDDDDDDZZ] Z: zeroed 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 leave an written extent from A to N. 0 A B N [UUWWWWWWWWWW] on-disk extent W: written extent [UUUUUUUUUUUU] extent status tree [--DDDDDDDDZZ] Finally ext4_map_create_blocks() only insert extent A to B to the extent status tree, and leave an stale unwritten extent in the status tree. 0 A B N [UUWWWWWWWWWW] on-disk extent W: written extent [UUWWWWWWWWUU] extent status tree [--DDDDDDDDZZ] Fix this issue by always cached extent status entry after zeroing out the second part. Signed-off-by: Zhang Yi <yi.zhang@huawei.com> Reviewed-by: Baokun Li <libaokun1@huawei.com> Cc: stable@kernel.org Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> Message-ID: <20251129103247.686136-7-yi.zhang@huaweicloud.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Yang Erkun <yangerkun@huawei.com> Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/ext4/extents.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 9476c1c7e9be..0bb9730f8cf9 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3340,8 +3340,16 @@ static int ext4_split_extent_at(handle_t *handle, * extent length and ext4_split_extent() split will the * first half again. */ - if (split_flag & EXT4_EXT_DATA_PARTIAL_VALID1) + if (split_flag & EXT4_EXT_DATA_PARTIAL_VALID1) { + /* + * Drop extent cache to prevent stale unwritten + * extents remaining after zeroing out. + */ + ext4_es_remove_extent(inode, + le32_to_cpu(zero_ex.ee_block), + ext4_ext_get_actual_len(&zero_ex)); goto fix_extent_len; + } /* update the extent length and mark as initialized */ ex->ee_len = cpu_to_le16(ee_len); -- 2.52.0
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