From bcd8e91f98c156f4b1ebcfacae675f9cfd962441 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sat, 1 Sep 2018 12:45:04 -0400 Subject: ext4: avoid arithemetic overflow that can trigger a BUG 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 Reported-by: Wen Xu Cc: stable@vger.kernel.org --- fs/ext4/inode.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'fs/ext4/inode.c') diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 8f6ad7667974..694f31364206 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3412,12 +3412,16 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, { struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); unsigned int blkbits = inode->i_blkbits; - unsigned long first_block = offset >> blkbits; - unsigned long last_block = (offset + length - 1) >> blkbits; + unsigned long first_block, last_block; struct ext4_map_blocks map; bool delalloc = false; int ret; + if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK) + return -EINVAL; + first_block = offset >> blkbits; + last_block = min_t(loff_t, (offset + length - 1) >> blkbits, + EXT4_MAX_LOGICAL_BLOCK); if (flags & IOMAP_REPORT) { if (ext4_has_inline_data(inode)) { -- cgit v1.2.3