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Tue, 14 Apr 2026 06:25:04 -0700 (PDT) Received: from mi-HP-ProDesk-680-G6-PCI-Microtower-PC ([43.224.245.229]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c7921a12adasm12526545a12.26.2026.04.14.06.24.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2026 06:25:02 -0700 (PDT) From: Ziqing Chen X-Google-Original-From: Ziqing Chen To: tiwai@suse.com, perex@perex.cz Cc: linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Ziqing Chen Subject: [PATCH v2] ALSA: control: Validate buf_len before strnlen() in snd_ctl_elem_init_enum_names() Date: Tue, 14 Apr 2026 21:24:37 +0800 Message-ID: <20260414132437.261304-1-chenziqing@xiaomi.com> X-Mailer: git-send-email 2.50.1 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" snd_ctl_elem_init_enum_names() advances pointer p through the names buffer while decrementing buf_len. If buf_len reaches zero but items remain, the next iteration calls strnlen(p, 0). While strnlen(p, 0) returns 0 and would hit the existing name_len =3D=3D 0 error path, CONFIG_FORTIFY_SOURCE's fortified strnlen() first checks maxlen against __builtin_dynamic_object_size(). When Clang loses track of p's object size inside the loop, this triggers a BRK exception panic before the return value is examined. Add a buf_len =3D=3D 0 guard at the loop entry to prevent calling fortified strnlen() on an exhausted buffer. Found by kernel fuzz testing through Xiaomi Smartphone. Fixes: 8d448162bda5 ("ALSA: control: add support for ENUMERATED user space = controls") Cc: stable@vger.kernel.org Signed-off-by: Ziqing Chen --- sound/core/control.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/sound/core/control.c b/sound/core/control.c index 0ddade871b52..6ceb5f977fcd 100644 --- a/sound/core/control.c +++ b/sound/core/control.c @@ -1574,6 +1574,10 @@ static int snd_ctl_elem_init_enum_names(struct user_= element *ue) /* check that there are enough valid names */ p =3D names; for (i =3D 0; i < ue->info.value.enumerated.items; ++i) { + if (buf_len =3D=3D 0) { + kvfree(names); + return -EINVAL; + } name_len =3D strnlen(p, buf_len); if (name_len =3D=3D 0 || name_len >=3D 64 || name_len =3D=3D buf_len) { kvfree(names); -- 2.52.0