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Sun, 7 Jun 2026 07:24:34 +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 m978HrIcJWqSOgAAD6G6ig (envelope-from ); Sun, 07 Jun 2026 07:24:34 +0000 Date: Sun, 07 Jun 2026 09:24:34 +0200 Message-ID: <87ik7usthp.wl-tiwai@suse.de> From: Takashi Iwai To: Kyle Zeng Cc: linux-sound@vger.kernel.org, tiwai@suse.de Subject: Re: [PATCH] ALSA: seq: Clear variable event pointer on read In-Reply-To: <20260607004129.61345-1-kylebot@openai.com> References: <20260607004129.61345-1-kylebot@openai.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-Rspamd-Action: no action X-Rspamd-Queue-Id: A44616A887 X-Spam-Flag: NO X-Spam-Score: -3.51 X-Spam-Level: X-Spamd-Result: default: False [-3.51 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; 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)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received,2a07:de40:b281:104:10:150:64:97:from]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.de:dkim]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org On Sun, 07 Jun 2026 02:41:29 +0200, Kyle Zeng wrote: > > snd_seq_read() copies a queued variable-length event header to userspace > before expanding the payload. Queued variable-length events use > SNDRV_SEQ_EXT_CHAINED internally, and data.ext.ptr points at the first > extension cell. > > The read side strips SNDRV_SEQ_EXT_* bits from data.ext.len before the > copy, but it leaves data.ext.ptr untouched. A userspace sequencer client > can therefore write a direct variable event to itself and read back the > extension-cell kernel address from the returned header. > > Clear the temporary header pointer before copy_to_user(). The original > queued event remains unchanged and is still passed to > snd_seq_expand_var_event(), so payload expansion keeps using the > internal chain. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Kyle Zeng Applied to for-next branch now. Thanks. Takashi