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Thu, 30 Apr 2026 06:07:34 +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 6J6FD6bx8mnKdwAAD6G6ig (envelope-from ); Thu, 30 Apr 2026 06:07:34 +0000 Date: Thu, 30 Apr 2026 08:07:33 +0200 Message-ID: <87pl3hnfq2.wl-tiwai@suse.de> From: Takashi Iwai To: songxiebing Cc: tiwai@suse.com, perex@perex.cz, linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+ee73befabe68e7907adf@syzkaller.appspotmail.com Subject: Re: [PATCH] ALSA: pcm_oss: Fix use-after-free in poll via io_uring In-Reply-To: <20260430021401.181505-1-songxiebing@kylinos.cn> References: <20260430021401.181505-1-songxiebing@kylinos.cn> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/30.2 Mule/6.0 Precedence: bulk X-Mailing-List: linux-kernel@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-Score: -1.80 X-Spam-Level: X-Spamd-Result: default: False [-1.80 / 50.00]; BAYES_HAM(-3.00)[99.99%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; TO_DN_SOME(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; TAGGED_RCPT(0.00)[ee73befabe68e7907adf]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_FIVE(0.00)[6]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[kylinos.cn:email,imap1.dmz-prg2.suse.org:helo,appspotmail.com:email,suse.de:mid] X-Spam-Flag: NO On Thu, 30 Apr 2026 04:14:01 +0200, songxiebing wrote: > > From: Bob Song > > Fix use-after-free bug in snd_pcm_oss_poll() caused by > io_uring asynchronous poll operations accessing already-freed > pcm_oss_file private data. > > The bug happens because file->private_data still points to > kfree()'d memory after snd_pcm_oss_release(), and io_uring > may invoke ->poll() handler later. > > Fix by: > 1. Clearing file->private_data early in release function > 2. Adding NULL check in release to avoid invalid access > 3. Adding NULL check in poll handler to prevent UAF > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") /* pcm_oss initial */ > Reported-by: syzbot+ee73befabe68e7907adf@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/alsa-devel/000000000000f1068105f20e5e8f@google.com/ This is a very old report. Are you sure that it's still valid with the latest kernel? I believe this kind of bug should have been already fixed. (And above all, the suggested code change doesn't look enough as a proper fix.) The same question applied for your other two patches for rawmidi and PCM UAFs. thanks, Takashi