A maliciously crafted file system can cause an overflow when the results of a 64-bit calculation is stored into a 32-bit length parameter. https://bugzilla.kernel.org/show_bug.cgi?id=200623 Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Reported-by: Wen Xu <wen.xu@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- fs/ext4/inode.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 8f6ad7667974..1134c3473673 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3414,6 +3414,7 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, unsigned int blkbits = inode->i_blkbits; unsigned long first_block = offset >> blkbits; unsigned long last_block = (offset + length - 1) >> blkbits; + unsigned long len; struct ext4_map_blocks map; bool delalloc = false; int ret; @@ -3434,7 +3435,8 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, } map.m_lblk = first_block; - map.m_len = last_block - first_block + 1; + len = last_block - first_block + 1; + map.m_len = (len < UINT_MAX) ? len : UINT_MAX; if (flags & IOMAP_REPORT) { ret = ext4_map_blocks(NULL, inode, &map, 0); -- 2.18.0.rc0
