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dm-pcache: fix implicit u8 truncation of gc_percent in message handler

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When setting gc_percent via message, kstrtoul parses the input into an
unsigned long, which is then implicitly truncated to u8 when passed to
pcache_cache_set_gc_percent(). For example, value 266 (0x10A) silently
truncates to 10 (0x0A), successfully bypassing the > 90 upper bound
check in pcache_cache_set_gc_percent(), and setting a different value
than the user intended.

Use kstrtou8 directly instead of kstrtoul, so that overflow values are
properly rejected.

Cc: stable@vger.kernel.org
Fixes: 1d57628ff9 ("dm-pcache: add persistent cache target in device-mapper")
Signed-off-by: Jianyun Gao <jianyungao89@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This commit is contained in:
Jianyun Gao 2026-07-20 17:46:48 +08:00 committed by Mikulas Patocka
parent 73c37fe54c
commit fb9e17287a
1 changed files with 2 additions and 2 deletions
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4
drivers/md/dm-pcache/dm_pcache.c
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@ -439,13 +439,13 @@ static int dm_pcache_message(struct dm_target *ti, unsigned int argc,
char **argv, char *result, unsigned int maxlen)
{
struct dm_pcache *pcache = ti->private;
unsigned long val;
u8 val;
if (argc != 2)
goto err;
if (!strcasecmp(argv[0], "gc_percent")) {
if (kstrtoul(argv[1], 10, &val))
if (kstrtou8(argv[1], 10, &val))
goto err;
return pcache_cache_set_gc_percent(&pcache->cache, val);