In order to avoid the below overflow issue, we should have checked the
boundaries in superblock before reaching out to allocation. As Linus suggested,
the right place should be sanity_check_raw_super().
Dr Silvio Cesare of InfoSect reported:
There are integer overflows with using the cp_payload superblock field in the
f2fs filesystem potentially leading to memory corruption.
include/linux/f2fs_fs.h
struct f2fs_super_block {
...
__le32 cp_payload;
fs/f2fs/f2fs.h
typedef u32 block_t; /*
* should not change u32, since it is the on-disk block
* address format, __le32.
*/
...
static inline block_t __cp_payload(struct f2fs_sb_info *sbi)
{
return le32_to_cpu(F2FS_RAW_SUPER(sbi)->cp_payload);
}
fs/f2fs/checkpoint.c
block_t start_blk, orphan_blocks, i, j;
...
start_blk = __start_cp_addr(sbi) + 1 + __cp_payload(sbi);
orphan_blocks = __start_sum_addr(sbi) - 1 - __cp_payload(sbi);
+++ integer overflows
...
unsigned int cp_blks = 1 + __cp_payload(sbi);
...
sbi->ckpt = kzalloc(cp_blks * blk_size, GFP_KERNEL);
+++ integer overflow leading to incorrect heap allocation.
int cp_payload_blks = __cp_payload(sbi);
...
ckpt->cp_pack_start_sum = cpu_to_le32(1 + cp_payload_blks +
orphan_blocks);
+++ sign bug and integer overflow
...
for (i = 1; i < 1 + cp_payload_blks; i++)
+++ integer overflow
...
sbi->max_orphans = (sbi->blocks_per_seg - F2FS_CP_PACKS -
NR_CURSEG_TYPE - __cp_payload(sbi)) *
F2FS_ORPHANS_PER_BLOCK;
+++ integer overflow
Reported-by: Greg KH <greg@kroah.com>
Reported-by: Silvio Cesare <silvio.cesare@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
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