The le64_to_cpu() forces the calculation to be unsigned, with the effect that it can underflow leading to an incorrect large value. This bug only triggers in rare(ish) circumstances, an empty file encoded as an extended regular file or a completely sparse file. Normally empty files are encoded as a regular file rather than as an extended regular file (and the regular file i_blocks calculation doesn't have this bug). To save space regular file inodes are optimised to encode the most commonly occurring files. Less common regular files are encoded using extended regular file inodes which contain extra information. Empty files with nlinks greater than 1, and or empty files with extended attributes are encoded using extended regular file inodes and they will hit this bug. Signed-off-by: Phillip Lougher <phillip@xxxxxxxxxxxxxxx> --- fs/squashfs/inode.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/squashfs/inode.c b/fs/squashfs/inode.c index fd7b3b3..81afbcc 100644 --- a/fs/squashfs/inode.c +++ b/fs/squashfs/inode.c @@ -208,8 +208,8 @@ int squashfs_read_inode(struct inode *inode, long long ino) inode->i_op = &squashfs_inode_ops; inode->i_fop = &generic_ro_fops; inode->i_mode |= S_IFREG; - inode->i_blocks = ((inode->i_size - - le64_to_cpu(sqsh_ino->sparse) - 1) >> 9) + 1; + inode->i_blocks = (inode->i_size - + le64_to_cpu(sqsh_ino->sparse) + 511) >> 9; squashfs_i(inode)->fragment_block = frag_blk; squashfs_i(inode)->fragment_size = frag_size; -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
