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Tue, 19 May 2026 05:39:37 +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 QfTHBpn3C2rDZAAAD6G6ig (envelope-from ); Tue, 19 May 2026 05:39:37 +0000 Date: Tue, 19 May 2026 07:39:28 +0200 Message-ID: <87cxys3qlr.wl-tiwai@suse.de> From: Takashi Iwai To: Maoyi Xie Cc: Takashi Iwai , Jaroslav Kysela , linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] ALSA: avoid past-the-end iterators in timer/seq port registration In-Reply-To: <20260518194023.1667857-1-maoyixie.tju@gmail.com> References: <87o6ic4izy.wl-tiwai@suse.de> <20260518194023.1667857-1-maoyixie.tju@gmail.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-Spam-Level: X-Rspamd-Action: no action X-Spamd-Result: default: False [-2.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; 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]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FREEMAIL_TO(0.00)[gmail.com]; 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)[]; RCPT_COUNT_FIVE(0.00)[5]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:dkim,suse.de:mid] X-Rspamd-Queue-Id: 398AF67381 X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Score: -2.01 On Mon, 18 May 2026 21:40:21 +0200, Maoyi Xie wrote: > > Two fixes in sound/core that remove past-the-end iterator > use of the shape > > list_for_each_entry(iter, head, member) { > if (...) break; > } > list_add_tail(&new, &iter->member); > > When the loop walks all entries without break, iter is past > the end and &iter->member aliases the list head via > container_of offset cancellation. The insert lands at the > list tail, which is the intended behaviour, but the access > is undefined per C11. > > Takashi Iwai confirmed on the inquiry thread that both sites > are bugs introduced by commit 9244b2c3079f ("[ALSA] alsa core: > convert to list_for_each_entry*"). The original list_for_each() > loop terminated at the list head; the conversion to > list_for_each_entry() left the post-loop access using the > container struct, which aliases the head via offset > cancellation. > > The patched code tracks an explicit insert_before pointer > initialised to the list head and overwritten to &iter->member > only when the loop breaks early. Observable behaviour is > unchanged. > > Inquiry thread: > https://lore.kernel.org/linux-sound/?q=iterator+used+after+loop+end+in+timer > > Maoyi Xie (2): > ALSA: timer: avoid past-the-end iterator in snd_timer_dev_register() > ALSA: seq: avoid past-the-end iterator in snd_seq_create_port() Applied both patches now. Thanks. Takashi