dm-pcache: reject option groups without values

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@trailofbits.com>
Reviewed-by:  Zheng Gu <cengku@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 1d57628ff95b ("dm-pcache: add persistent cache target in device-mapper")
Cc: stable@vger.kernel.org

diff --git a/drivers/md/dm-pcache/dm_pcache.c b/drivers/md/dm-pcache/dm_pcache.c
index 81c795c0400e930f19651ef0902547892ea342a4..d5cfd162c06335d7459f71fb02df220ce0355545 100644 (file)
--- 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;