Commit 60c672b7 authored by Kemeng Shi's avatar Kemeng Shi Committed by Theodore Ts'o
Browse files

ext4: avoid potential data overflow in next_linear_group 



ngroups is ext4_group_t (unsigned int) while next_linear_group treat it
in int. If ngroups is bigger than max number described by int, it will
be treat as a negative number. Then "return group + 1 >= ngroups ? 0 :
group + 1;" may keep returning 0.
Switch int to ext4_group_t in next_linear_group to fix the overflow.

Fixes: 196e402a ("ext4: improve cr 0 / cr 1 group scanning")
Signed-off-by: default avatarKemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20230801143204.2284343-3-shikemeng@huaweicloud.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent a9ce5993

fs/ext4/mballoc.c

+3 −2
Original line number Diff line number Diff line
@@ -1080,8 +1080,9 @@ static inline int should_optimize_scan(struct ext4_allocation_context *ac) 
 * Return next linear group for allocation. If linear traversal should not be

 * performed, this function just returns the same group

 */

static int

next_linear_group(struct ext4_allocation_context *ac, int group, int ngroups)

static ext4_group_t

next_linear_group(struct ext4_allocation_context *ac, ext4_group_t group,

		  ext4_group_t ngroups)

{

	if (!should_optimize_scan(ac))

		goto inc_and_return;