The problem was in calculate_skip() function.

int skip = calculate_skip(i_size_read(inode) >> msblk->block_log);

i_size_read(inode) and msblk->block_log are unsigned integers, but calculate_skip had a signed int as argument. This cast led to wrong skip value and then to divide by zero bug.

Fixes: 1701aecb6849 ("Squashfs: regular file operations") Cc: stable@vger.kernel.org Reported-by: syzbot+e8f781243ce16ac2f962@syzkaller.appspotmail.com Signed-off-by: Pavel Skripkin paskripkin@gmail.com --- fs/squashfs/file.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c index 7b1128398976..2ebcbd4f84cc 100644 --- a/fs/squashfs/file.c +++ b/fs/squashfs/file.c @@ -44,8 +44,8 @@ * Locate cache slot in range [offset, index] for specified inode. If * there's more than one return the slot closest to index. */ -static struct meta_index *locate_meta_index(struct inode *inode, int offset, - int index) +static struct meta_index *locate_meta_index(struct inode *inode, unsigned int offset, + unsigned int index) { struct meta_index *meta = NULL; struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; @@ -83,8 +83,8 @@ static struct meta_index *locate_meta_index(struct inode *inode, int offset, /* * Find and initialise an empty cache slot for index offset. */ -static struct meta_index *empty_meta_index(struct inode *inode, int offset, - int skip) +static struct meta_index *empty_meta_index(struct inode *inode, unsigned int offset, + unsigned int skip) { struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; struct meta_index *meta = NULL; @@ -211,11 +211,11 @@ static long long read_indexes(struct super_block *sb, int n, * If the skip factor is limited in this way then the file will use multiple * slots. */ -static inline int calculate_skip(int blocks) +static inline unsigned int calculate_skip(unsigned int blocks) { - int skip = blocks / ((SQUASHFS_META_ENTRIES + 1) + unsigned int skip = blocks / ((SQUASHFS_META_ENTRIES + 1) * SQUASHFS_META_INDEXES); - return min(SQUASHFS_CACHED_BLKS - 1, skip + 1); + return min((unsigned int) SQUASHFS_CACHED_BLKS - 1, skip + 1); }

@@ -224,12 +224,12 @@ static inline int calculate_skip(int blocks) * on-disk locations of the datablock and block list metadata block * <index_block, index_offset> for index (scaled to nearest cache index). */ -static int fill_meta_index(struct inode *inode, int index, +static int fill_meta_index(struct inode *inode, unsigned int index, u64 *index_block, int *index_offset, u64 *data_block) { struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; - int skip = calculate_skip(i_size_read(inode) >> msblk->block_log); - int offset = 0; + unsigned int skip = calculate_skip(i_size_read(inode) >> msblk->block_log); + unsigned int offset = 0; struct meta_index *meta; struct meta_entry *meta_entry; u64 cur_index_block = squashfs_i(inode)->block_list_start; @@ -323,7 +323,7 @@ static int fill_meta_index(struct inode *inode, int index, * Get the on-disk location and compressed size of the datablock * specified by index. Fill_meta_index() does most of the work. */ -static int read_blocklist(struct inode *inode, int index, u64 *block) +static int read_blocklist(struct inode *inode, unsigned int index, u64 *block) { u64 start; long long blks; @@ -448,7 +448,7 @@ static int squashfs_readpage(struct file *file, struct page *page) { struct inode *inode = page->mapping->host; struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info; - int index = page->index >> (msblk->block_log - PAGE_SHIFT); + unsigned int index = page->index >> (msblk->block_log - PAGE_SHIFT); int file_end = i_size_read(inode) >> msblk->block_log; int expected = index == file_end ? (i_size_read(inode) & (msblk->block_size - 1)) :