[Devel] [PATCH vz10 22/24] dm-qcow2: fix ALLOW_ERROR_INJECTION class on qcow2_alloc_delta (ERRNO not NULL)

[Konstantin Khorenko]

qcow2_alloc_delta() returns a valid pointer or ERR_PTR(-ENOMEM); it never
returns NULL, and its only caller qcow2_ctr() checks IS_ERR() only, then
dereferences the result (qcow2->img_id = i). It was annotated
ALLOW_ERROR_INJECTION(..., NULL), whose default injected return value is 0
(NULL), which slips past the IS_ERR() check and NULL-derefs. Use ERRNO
(error pointers only), matching the function's contract and the caller's
handling. Same class of bug as the dm-ploop ploop_get_delta_file fix.

Fixes: 538ef4c12f46 ("dm-qcow2: Enable injection fault")
Feature: dm-qcow2: block device over QCOW2 files driver
https://virtuozzo.atlassian.net/browse/VSTOR-137234
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 drivers/md/dm-qcow2-target.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-qcow2-target.c b/drivers/md/dm-qcow2-target.c
index 3f65897ce9da..de1fb628735b 100644
--- a/drivers/md/dm-qcow2-target.c
+++ b/drivers/md/dm-qcow2-target.c
@@ -678,7 +678,7 @@ static struct qcow2 *qcow2_alloc_delta(struct qcow2_target *tgt, struct qcow2 *u
 
 	return qcow2;
 }
-ALLOW_ERROR_INJECTION(qcow2_alloc_delta, NULL);
+ALLOW_ERROR_INJECTION(qcow2_alloc_delta, ERRNO);
 
 static int qcow2_attach_file(struct dm_target *ti, struct qcow2_target *tgt,
 			     struct qcow2 *qcow2, int fd)
-- 
2.47.1