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Mon, 20 Jul 2026 02:46:56 -0700 (PDT) Received: from DESKTOP-P5RIK7I.localdomain ([118.112.177.142]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2cf346d9ba9sm54406335ad.48.2026.07.20.02.46.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jul 2026 02:46:56 -0700 (PDT) From: jianyungao89@gmail.com To: dm-devel@lists.linux.dev Cc: Jianyun Gao , Dongsheng Yang , Zheng Gu , linux-kernel@vger.kernel.org (open list) Subject: [PATCH] dm-pcache: fix implicit u8 truncation of gc_percent in message handler Date: Mon, 20 Jul 2026 17:46:48 +0800 Message-Id: <20260720094649.10104-1-jianyungao89@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Jianyun Gao 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. Signed-off-by: Jianyun Gao --- drivers/md/dm-pcache/dm_pcache.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-pcache/dm_pcache.c b/drivers/md/dm-pcache/dm_pca= che.c index d5cfd162c063..645fc27d82ba 100644 --- a/drivers/md/dm-pcache/dm_pcache.c +++ b/drivers/md/dm-pcache/dm_pcache.c @@ -439,13 +439,13 @@ static int dm_pcache_message(struct dm_target *ti, un= signed int argc, char **argv, char *result, unsigned int maxlen) { struct dm_pcache *pcache =3D ti->private; - unsigned long val; + u8 val; =20 if (argc !=3D 2) goto err; =20 if (!strcasecmp(argv[0], "gc_percent")) { - if (kstrtoul(argv[1], 10, &val)) + if (kstrtou8(argv[1], 10, &val)) goto err; =20 return pcache_cache_set_gc_percent(&pcache->cache, val); --=20 2.34.1