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[v3,02/10] ext4: avoid potential data overflow in next_linear_group

Message ID 20230801143204.2284343-3-shikemeng@huaweicloud.com
State Awaiting Upstream
Headers show
Series A few fixes and cleanups to mballoc | expand

Commit Message

Kemeng Shi Aug. 1, 2023, 2:31 p.m. UTC 
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: 196e402adf2e ("ext4: improve cr 0 / cr 1 group scanning")
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 fs/ext4/mballoc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
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Patch

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 556b7cd27f76..a6635cba291a 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -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;