The function has a memory leak when kvrealloc() fails. The function directly assigns NULL to the markers pointer, losing the reference to the previously allocated memory. This causes kvfree() in pt_dump_init() to free NULL instead of the leaked memory.
Fix by: 1. Using kvrealloc() uniformly for all allocations 2. Using a temporary variable to preserve the original pointer until allocation succeeds 3. Removing the error path that sets markers_cnt=0 to keep consistency between markers and markers_cnt
Found via static analysis and this is similar to commit 42378a9ca553 ("bpf, verifier: Fix memory leak in array reallocation for stack state")
Fixes: d0e7915d2ad3 ("s390/mm/ptdump: Generate address marker array dynamically") Cc: stable@vger.kernel.org Signed-off-by: Miaoqian Lin linmq006@gmail.com --- changes in v2: - update the fixing logic to prevent memory leak in v1 v1 link: https://lore.kernel.org/all/20251026091351.36275-1-linmq006@gmail.com/ --- arch/s390/mm/dump_pagetables.c | 22 +++++++++------------- 1 file changed, 9 insertions(+), 13 deletions(-)
diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c index 9af2aae0a515..ab0c1fcf2782 100644 --- a/arch/s390/mm/dump_pagetables.c +++ b/arch/s390/mm/dump_pagetables.c @@ -291,16 +291,15 @@ static int ptdump_cmp(const void *a, const void *b)
static int add_marker(unsigned long start, unsigned long end, const char *name) { - size_t oldsize, newsize; - - oldsize = markers_cnt * sizeof(*markers); - newsize = oldsize + 2 * sizeof(*markers); - if (!oldsize) - markers = kvmalloc(newsize, GFP_KERNEL); - else - markers = kvrealloc(markers, newsize, GFP_KERNEL); - if (!markers) - goto error; + struct addr_marker *new_markers; + size_t newsize; + + newsize = (markers_cnt + 2) * sizeof(*markers); + new_markers = kvrealloc(markers, newsize, GFP_KERNEL); + if (!new_markers) + return -ENOMEM; + + markers = new_markers; markers[markers_cnt].is_start = 1; markers[markers_cnt].start_address = start; markers[markers_cnt].size = end - start; @@ -312,9 +311,6 @@ static int add_marker(unsigned long start, unsigned long end, const char *name) markers[markers_cnt].name = name; markers_cnt++; return 0; -error: - markers_cnt = 0; - return -ENOMEM; }
static int pt_dump_init(void)