Currently ext4 directory handling code implicitly assumes that the directory blocks are always within the i_size. In fact ext4_append() will attempt to allocate next directory block based solely on i_size and the i_size is then appropriately increased after a successful allocation.
However, for this to work it requires i_size to be correct. If, for any reason, the directory inode i_size is corrupted in a way that the directory tree refers to a valid directory block past i_size, we could end up corrupting parts of the directory tree structure by overwriting already used directory blocks when modifying the directory.
Fix it by catching the corruption early in __ext4_read_dirblock().
Signed-off-by: Lukas Czerner lczerner@redhat.com Addresses Red-Hat-Bugzilla: #2070205 Cc: stable@vger.kernel.org --- fs/ext4/namei.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index db4ba99d1ceb..cf460aa4f81d 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -110,6 +110,13 @@ static struct buffer_head *__ext4_read_dirblock(struct inode *inode, struct ext4_dir_entry *dirent; int is_dx_block = 0;
+ if (block >= inode->i_size) { + ext4_error_inode(inode, func, line, block, + "Attempting to read directory block (%u) that is past i_size (%llu)", + block, inode->i_size); + return ERR_PTR(-EFSCORRUPTED); + } + if (ext4_simulate_fail(inode->i_sb, EXT4_SIM_DIRBLOCK_EIO)) bh = ERR_PTR(-EIO); else
On Jul 4, 2022, at 8:27 AM, Lukas Czerner lczerner@redhat.com wrote:
Currently ext4 directory handling code implicitly assumes that the directory blocks are always within the i_size. In fact ext4_append() will attempt to allocate next directory block based solely on i_size and the i_size is then appropriately increased after a successful allocation.
However, for this to work it requires i_size to be correct. If, for any reason, the directory inode i_size is corrupted in a way that the directory tree refers to a valid directory block past i_size, we could end up corrupting parts of the directory tree structure by overwriting already used directory blocks when modifying the directory.
Fix it by catching the corruption early in __ext4_read_dirblock().
Signed-off-by: Lukas Czerner lczerner@redhat.com
Reviewed-by: Andreas Dilger adilger@dilger.ca
Addresses Red-Hat-Bugzilla: #2070205 Cc: stable@vger.kernel.org
fs/ext4/namei.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index db4ba99d1ceb..cf460aa4f81d 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -110,6 +110,13 @@ static struct buffer_head *__ext4_read_dirblock(struct inode *inode, struct ext4_dir_entry *dirent; int is_dx_block = 0;
- if (block >= inode->i_size) {
ext4_error_inode(inode, func, line, block,"Attempting to read directory block (%u) that is past i_size (%llu)",block, inode->i_size);return ERR_PTR(-EFSCORRUPTED);- }
- if (ext4_simulate_fail(inode->i_sb, EXT4_SIM_DIRBLOCK_EIO)) bh = ERR_PTR(-EIO); else
-- 2.35.3
Cheers, Andreas
On Mon, 4 Jul 2022 16:27:20 +0200, Lukas Czerner wrote:
Currently ext4 directory handling code implicitly assumes that the directory blocks are always within the i_size. In fact ext4_append() will attempt to allocate next directory block based solely on i_size and the i_size is then appropriately increased after a successful allocation.
However, for this to work it requires i_size to be correct. If, for any reason, the directory inode i_size is corrupted in a way that the directory tree refers to a valid directory block past i_size, we could end up corrupting parts of the directory tree structure by overwriting already used directory blocks when modifying the directory.
[...]
Applied, thanks!
[1/2] ext4: check if directory block is within i_size commit: 65d23bd6e76ae07cee50c24d1fbeea4044aa41e7 [2/2] ext4: make sure ext4_append() always allocates new block commit: 6d3ab9450ea5ec08882ab2f255827f1a39e300de
Best regards,
linux-stable-mirror@lists.linaro.org
-
Andreas Dilger -
Lukas Czerner -
Theodore Ts'o