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Date: Mon, 4 Jul 2022 16:27:20 +0200 From: Lukas Czerner <lczerner@...hat.com> To: linux-ext4@...r.kernel.org Cc: tytso@....edu, stable@...r.kernel.org Subject: [PATCH 1/2] ext4: check if directory block is within i_size 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@...hat.com> Addresses Red-Hat-Bugzilla: #2070205 Cc: stable@...r.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
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