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Wed, 4 Nov 2026 07:19:51 +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 ZboCAZfc6mr1MAAAD6G6ig (envelope-from ); Wed, 04 Nov 2026 07:19:51 +0000 Date: Wed, 04 Nov 2026 08:19:50 +0100 Message-ID: <87se1hukq1.wl-tiwai@suse.de> From: Takashi Iwai To: Sinan Turunc Cc: Jaroslav Kysela , Takashi Iwai , linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] ALSA: usx2y: Reject buffers smaller than two packets In-Reply-To: <20261103132247.713-1-enscrpt@pm.me> References: <20261103132247.713-1-enscrpt@pm.me> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/30.2 Mule/6.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 877451F79F X-Spam-Level: X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Flag: NO X-Spamd-Result: default: False [-12.51 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; 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)[]; URIBL_BLOCKED(0.00)[suse.de:dkim,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,pm.me:email]; MIME_TRACE(0.00)[0:+]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_DN_SOME(0.00)[]; ARC_NA(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; RCPT_COUNT_FIVE(0.00)[6]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received,2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.de:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Spam-Score: -12.51 On Tue, 03 Nov 2026 14:23:03 +0100, Sinan Turunc wrote: > > usx2y_urb_capt_retire() splits the copy into the ALSA ring buffer once > at the buffer end and wraps hwptr_done once, which is only correct when > one packet holds at most buffer_size frames. The packet size is the > endpoint's maxpacksize from usb_maxpacket(), while the hw constraints > allow 64-byte periods with periods_min 2, so a packet can be larger than > the whole buffer. > > The endpoint is known at probe time, so constrain > SNDRV_PCM_HW_PARAM_BUFFER_BYTES in snd_usx2y_pcm_open() to at least > twice the endpoint's packet size. Two packets, matching the line6 fix. > The bound makes the copy safe, but it does not make every larger buffer > progress: the position is reported once per URB of 4 packets, so a > buffer that divides one URB's data returns to the same position at every > callback. That was already the case before this patch and is not changed > here. Keep a guard in usx2y_urb_capt_retire() that drops an oversized > packet with a ratelimited error, for the case that should no longer be > reachable. > > Reproduced on 7.3-rc7 with a USB/IP device presenting the US-122 > interface layout and 1024-byte packets into a 512-byte buffer: > > BUG: KASAN: out-of-bounds in i_usx2y_urb_complete+0x1285/0x1ac0 > Read of size 18446744073709551104 at addr ffff88800e448800 by task vhci_rx/83 > > With this patch a 1024-byte buffer is refused at hw_params; a 2048-byte > buffer is accepted and safe but barely advances (hw_ptr 9216 after 30 s, > for the reason above); a 3072-byte buffer streams for 30 s with no > report and with the position moving inside the buffer. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Cc: stable@vger.kernel.org > Signed-off-by: Sinan Turunc Applied now. thanks. Takashi