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 <tytso@mit.edu>
Reported-by: Wen Xu <wen.xu@gatech.edu>
Cc: stable@vger.kernel.org
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 249bcee..ac05bd8 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -686,6 +686,9 @@
/* 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
*/
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 8f6ad76..694f313 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3412,12 +3412,16 @@
{
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)) {