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Tue, 26 May 2026 05:28:05 +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 RbJPCGUvFWprDgAAD6G6ig (envelope-from ); Tue, 26 May 2026 05:28:05 +0000 Date: Tue, 26 May 2026 07:28:04 +0200 Message-ID: <871pey210b.wl-tiwai@suse.de> From: Takashi Iwai To: Jiakai Xu Cc: linux-kernel@vger.kernel.org, linux-sound@vger.kernel.org, Jaroslav Kysela , Kees Cook , Takashi Iwai Subject: Re: [PATCH] ALSA: pcm: Fix NULL dereference in import_ubuf() during exit In-Reply-To: <20260526013245.785435-1-xujiakai24@mails.ucas.ac.cn> References: <20260526013245.785435-1-xujiakai24@mails.ucas.ac.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: -3.30 X-Spamd-Result: default: False [-3.30 / 50.00]; BAYES_HAM(-3.00)[99.99%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.995]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; FUZZY_RATELIMITED(0.00)[rspamd.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_FIVE(0.00)[6]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,imap1.dmz-prg2.suse.org:helo,ucas.ac.cn:email] X-Spam-Level: X-Spam-Flag: NO On Tue, 26 May 2026 03:32:45 +0200, Jiakai Xu wrote: > > snd_pcm_oss_sync() calls snd_pcm_lib_write(substream, NULL, size) to > fill silence. The in_kernel flag is hard-coded to false by the wrapper, > so do_transfer() falls through to import_ubuf() with a garbage pointer > (NULL + frame_offset). When the process is in do_exit() and current->mm > is already NULL, import_ubuf()'s access_ok() crashes dereferencing > mm->context.pmlen. > > Add a NULL guard in do_transfer() to use iov_iter_kvec() with a dummy > kvec for the fill_silence path, avoiding the import_ubuf() call. The > fill_silence transfer function ignores the iov_iter, so the dummy kvec > is safe. > > Fixes: cf393babb37a1 ("ALSA: pcm: Add copy ops with iov_iter") > Signed-off-by: Jiakai Xu This is already fixed by the upstream commit e4d3386b74fb ("ALSA: pcm: Don't setup bogus iov_iter for silencing"). thanks, Takashi