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Fri, 12 Jun 2026 11:33:16 +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 sBdVFnzuK2rUeAAAD6G6ig (envelope-from ); Fri, 12 Jun 2026 11:33:16 +0000 Date: Fri, 12 Jun 2026 13:33:15 +0200 Message-ID: <877bo4hu2s.wl-tiwai@suse.de> From: Takashi Iwai To: HanQuan Cc: linux-sound@vger.kernel.org, tiwai@suse.de, perex@perex.cz Subject: Re: [PATCH] ALSA: seq: Fix kernel heap address leak in bounce_error_event() In-Reply-To: <20260612103222.2528305-1-eilaimemedsnaimel@gmail.com> References: <20260612103222.2528305-1-eilaimemedsnaimel@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-Flag: NO 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)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_TO(0.00)[gmail.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_THREE(0.00)[4]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,imap1.dmz-prg2.suse.org:helo] X-Spam-Level: X-Spam-Score: -3.30 On Fri, 12 Jun 2026 12:32:22 +0200, HanQuan wrote: > > The comment above bounce_error_event() documents that user clients > should receive SNDRV_SEQ_EVENT_BOUNCE with the original event embedded > as variable-length data, while kernel clients should receive > SNDRV_SEQ_EVENT_KERNEL_ERROR with a quoted kernel pointer. > > However, the implementation unconditionally uses > SNDRV_SEQ_EVENT_KERNEL_ERROR with data.quote.event set to the raw > struct snd_seq_event pointer for all clients. When a bounce error > event is delivered to a USER_CLIENT via snd_seq_read(), the kernel > heap address in data.quote.event is exposed to userspace through > copy_to_user() in the fixed-length branch. > > This is a distinct leak path from the one addressed by commit > 705dd6dcbc0e ("ALSA: seq: Clear variable event pointer on read"), > which sanitizes data.ext.ptr in the variable-length branch of > snd_seq_read(). The bounce_error_event() leak uses fixed-length > events that take the else branch where no sanitization occurs. > > Differentiate the bounce event by client type. For USER_CLIENT, > send SNDRV_SEQ_EVENT_BOUNCE with SNDRV_SEQ_EVENT_LENGTH_VARIABLE > and data.ext pointing to the original event. The variable-length > path in snd_seq_event_dup() copies the event data into chained > cells, and snd_seq_expand_var_event() copies only the content -- > never the pointer -- to userspace. For KERNEL_CLIENT, keep the > existing SNDRV_SEQ_EVENT_KERNEL_ERROR behavior with the quoted > pointer. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: HanQuan Applied to for-next branch now. Thanks. Takashi