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Tue, 14 Apr 2026 13:31:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id Lqq1MsdB3ml8RAAAD6G6ig (envelope-from ); Tue, 14 Apr 2026 13:31:51 +0000 Date: Tue, 14 Apr 2026 15:31:51 +0200 Message-ID: <87340xsm60.wl-tiwai@suse.de> From: Takashi Iwai To: Ziqing Chen Cc: tiwai@suse.com, perex@perex.cz, linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Ziqing Chen Subject: Re: [PATCH v2] ALSA: control: Validate buf_len before strnlen() in snd_ctl_elem_init_enum_names() In-Reply-To: <20260414132437.261304-1-chenziqing@xiaomi.com> References: <20260414132437.261304-1-chenziqing@xiaomi.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/30.2 Mule/6.0 Precedence: bulk X-Mailing-List: linux-sound@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Spamd-Result: default: False [-3.51 / 50.00]; BAYES_HAM(-3.00)[99.99%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FREEMAIL_TO(0.00)[gmail.com]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCPT_COUNT_SEVEN(0.00)[7]; RCVD_VIA_SMTP_AUTH(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.de:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.de:dkim,suse.de:mid] X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -3.51 X-Spam-Level: X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Queue-Id: 244D26A906 On Tue, 14 Apr 2026 15:24:37 +0200, Ziqing Chen wrote: > > 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 == 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 == 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 Applied now. Thanks. Takashi