[PATCH v3 1/3] md/raid5: set pool_size before extra_page allocation to fix leak on error path

[ghuicao@163.com]

From: Cao Guanghui <caoguanghui@kylinos.cn>

In setup_conf(), conf->disks is allocated with max_disks slots and
extra_page is allocated for each slot.  However, pool_size remains 0
(uninitialized from kzalloc) until grow_stripes() sets it later.  If
any allocation or initialization between the extra_page loop and
grow_stripes() fails and jumps to abort, free_conf() iterates
pool_size (= 0) times and skips the extra_page freeing loop entirely,
leaking max_disks pages.

Set pool_size to max_disks right after the disks array allocation
succeeds, so that free_conf() correctly frees all allocated
extra_page entries on any error path.  This is safe because:

- If kzalloc_objs(disks) fails, pool_size stays 0 and free_conf
  skips the loop (kfree(NULL) is safe).
- grow_stripes() later sets pool_size = devs, which equals max_disks,
  so the early assignment does not change the final value.
- resize_stripes() only updates pool_size on success and reallocates
  the disks array in lockstep.

Fixes: d7bd398e97f2 ("md/r5cache: handle alloc_page failure")
Cc: stable@vger.kernel.org
Signed-off-by: Cao Guanghui <caoguanghui@kylinos.cn>
---
 drivers/md/raid5.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7732,8 +7732,9 @@ static struct r5conf *setup_conf(struct mddev *mddev)
 	conf->disks = kzalloc_objs(struct disk_info, max_disks);
 
 	if (!conf->disks)
 		goto abort;
+	conf->pool_size = max_disks;
 
 	for (i = 0; i < max_disks; i++) {
 		conf->disks[i].extra_page = alloc_page(GFP_KERNEL);
 		if (!conf->disks[i].extra_page)
-- 
2.34.1