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Commit bcd8e91f authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

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: default avatarTheodore Ts'o <tytso@mit.edu>
Reported-by: default avatarWen Xu <wen.xu@gatech.edu>
Cc: stable@vger.kernel.org
parent 4d982e25

fs/ext4/ext4.h

+3 −0
Original line number Diff line number Diff line
@@ -686,6 +686,9 @@ enum { 
/* Max physical block we can address w/o extents */

#define EXT4_MAX_BLOCK_FILE_PHYS	0xFFFFFFFF



/* Max logical block we can support */

#define EXT4_MAX_LOGICAL_BLOCK		0xFFFFFFFF



/*

 * Structure of an inode on the disk

 */

fs/ext4/inode.c

+6 −2
Original line number Diff line number Diff line
@@ -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)) {