[PATCH v2] dm-pcache: reject option groups without values

[Samuel Moelius]

The pcache target parses optional arguments as name/value pairs.  A
table that advertises one optional argument and supplies only a
recognized option name, for example "cache_mode", reaches
parse_cache_opts() with argc == 1.  The parser consumes the name,
decrements argc to zero, then calls dm_shift_arg() again for the value.
dm_shift_arg() returns NULL when no arguments remain, and the following
strcmp() dereferences that NULL pointer.

Check that each recognized option has a value before consuming it.  This
keeps valid "cache_mode writeback" and "data_crc true/false" tables
unchanged while making malformed tables fail during target construction
with a precise missing-value error.

Assisted-by: Codex:gpt-5.5-cyber-preview
Signed-off-by: Samuel Moelius <sam.moelius@xxxxxxxxxxxxxxx>
---
Changes in v2:
  - Verify required arguments in a more flexible way

 drivers/md/dm-pcache/dm_pcache.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/md/dm-pcache/dm_pcache.c b/drivers/md/dm-pcache/dm_pcache.c
index 81c795c0400e..d5cfd162c063 100644
--- a/drivers/md/dm-pcache/dm_pcache.c
+++ b/drivers/md/dm-pcache/dm_pcache.c
@@ -168,6 +168,10 @@ static int parse_cache_opts(struct dm_pcache *pcache, struct dm_arg_set *as,
 		argc--;
 
 		if (!strcmp(arg, "cache_mode")) {
+			if (!argc) {
+				*error = "Missing value for cache_mode";
+				return -EINVAL;
+			}
 			arg = dm_shift_arg(as);
 			if (!strcmp(arg, "writeback")) {
 				opts->cache_mode = PCACHE_CACHE_MODE_WRITEBACK;
@@ -177,6 +181,10 @@ static int parse_cache_opts(struct dm_pcache *pcache, struct dm_arg_set *as,
 			}
 			argc--;
 		} else if (!strcmp(arg, "data_crc")) {
+			if (!argc) {
+				*error = "Missing value for data_crc";
+				return -EINVAL;
+			}
 			arg = dm_shift_arg(as);
 			if (!strcmp(arg, "true")) {
 				opts->data_crc = true;
-- 
2.43.0