From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794353513; b=wog8c7rB62buWOI5MA29ZBTLCpvr0Nqs6/FqMguyFev0zTeCfztm2eUdE2KwURPS3N8u TiWv6anqYEs858254fDK/Ldme9p3RyccXoKo90SRVFVXUFlSjUpgNUFMoC+qWAELltqw1 L3q2NEhwSErjFOg3DICgHeClRxbnwJgRgDvMEoUVolJTbFZYdS1tm338GSOtiTeKPUufp HvLwkLxkM2+tSUPEtdvLVRFN1n7Ya9CYUa/CcigmrtNbc6RCTp1fo7MzYBkB87zgIK8xe Qe+n/3q5iJ9oPsuaUuYhWziode7pPjGzrM7F4OAemDz1eEQ1iprz5orven4ivIx1OHw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794353513; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=1eJbvmIwPNaUQfAx///XZfvA4g45rOIfE3G2WKjM6ls=; b=BtVmlL8LspqTFqr5pLFnRrBMBTckiMjoD3k36Wc//+BW8fkMpnjG3Q67LxxubGc8XXOl khKDQ4638Cs9lFrrcXz6FoSXLUXFiqjBXWwz0sp4Ym6F2MxhGDrmf3AE4A4rSAW0HmoYp wS4IM6hCclSmusErBW1vD2pN/ordxO9AhRirg4MxLtmR7Hqbhy/aNc9QhaVB+u9asOm16 WIE9juVwYECZtARx5GGAHjGQR0vGVRqyHaoOKUF48oEFUlv5jHsgXRa2QcU85wr2Jbnat WXME0TT4R2jRgfEo1chB83/reEmukl8D6xpe2fk7jgBHPpkoJ+fNNzt1bMzCrK/roeQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=g5MW63Hk; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9346C606A31C for ; Tue, 10 Nov 2026 23:31:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=g5MW63Hk Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83F771F0093C; Tue, 10 Nov 2026 23:31:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794353513; bh=1eJbvmIwPNaUQfAx///XZfvA4g45rOIfE3G2WKjM6ls=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=g5MW63HkkpmOxUSFmID8e9M2/7600Q5lzg0Mc6IpK6hBMcEoiRxKfcee/DeXsL03R 3NyeyyZkCxnf9wPzJD5hfn5CZ/q6KlP2HQ7yQl8mt+ruQhz7Re75p8OUJBt0NXCo3p ouhKdRp+Ve7/VHruVQHBUyTlxhVkA9nEuHUjoxopUyBL37CAjobzvJvBLIvxj9hCy/ QzndF/gMYjaJn8Stz7HIplABP+/R4a4v3/ECmyHZl+a41JLdZhXnCyUYFqmSFuJ8ls 0FOEmbrjESiLQYwj0sY1o4XUAQQNh6ZOXrsHrqrMsFCx98NnRB1hPBzgHjYyqUwoU1 bRtvHCuBII88g== From: Sasha Levin To: stable@vger.kernel.org Cc: Takashi Iwai , Sashiko , Sasha Levin Subject: [PATCH 5.15.y] ALSA: emux: Fix UAF of soundfont zones at note-on Date: Tue, 10 Nov 2026 18:31:51 -0500 Message-ID: <20261110233132.129145-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107060910-failed-5.15-34e3e04b8a17@kernel.org> References: <20261107060910-failed-5.15-34e3e04b8a17@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Takashi Iwai [ Upstream commit 34e3e04b8a1731a773797542f0781e99ce7cd755 ] snd_emux_note_on() looks up the matching zones via snd_soundfont_search_zone(), which takes sflist->lock only during the lookup and returns the raw zone pointers after releasing it. The caller then stores them in vp->zone without any protection. Meanwhile, a concurrent SNDRV_EMUX_IOCTL_REMOVE_LAST_SAMPLES ioctl may unlink and free those zones in snd_soundfont_remove_unlocked(); this leads to a use-after-free in snd_emux_note_on(), and later at accessing the cached vp->zone, e.g. in snd_emux_send_effect(). Fix it by holding sflist->lock in snd_emux_note_on() over the whole zone lookup and voice setup, and let snd_soundfont_search_zone() require the caller to hold the lock, instead. snd_soundfont_lock_preset() takes sflist->lock for setting presets_locked, so the removal path now syncs with the note-on finish. Reported-by: Sashiko Closes: https://sashiko.dev/#/bug/linux-697212bb-a434-4ff5-8778-25a84f5dad89 Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20261020101624.205638-1-tiwai@suse.de Signed-off-by: Takashi Iwai [ sashal: replaced the scoped spinlock guard with explicit lock/unlock calls using a shared unlock path ] Signed-off-by: Sasha Levin --- sound/synth/emux/emux_synth.c | 9 +++++++-- sound/synth/emux/soundfont.c | 15 +++++++-------- 2 files changed, 14 insertions(+), 10 deletions(-) diff --git a/sound/synth/emux/emux_synth.c b/sound/synth/emux/emux_synth.c index a5385efcedb6c..195cb58fd428f 100644 --- a/sound/synth/emux/emux_synth.c +++ b/sound/synth/emux/emux_synth.c @@ -49,7 +49,7 @@ snd_emux_note_on(void *p, int note, int vel, struct snd_midi_channel *chan) int i, key, nvoices; struct snd_emux_voice *vp; struct snd_sf_zone *table[SNDRV_EMUX_MAX_MULTI_VOICES]; - unsigned long flags; + unsigned long flags, sf_flags; struct snd_emux_port *port; port = p; @@ -61,9 +61,12 @@ snd_emux_note_on(void *p, int note, int vel, struct snd_midi_channel *chan) return; key = note; /* remember the original note */ + + /* hold sflist->lock for protecting against concurrent free */ + spin_lock_irqsave(&emu->sflist->lock, sf_flags); nvoices = get_zone(emu, port, ¬e, vel, chan, table); if (! nvoices) - return; + goto unlock; /* exclusive note off */ for (i = 0; i < nvoices; i++) { @@ -136,6 +139,8 @@ snd_emux_note_on(void *p, int note, int vel, struct snd_midi_channel *chan) } } #endif +unlock: + spin_unlock_irqrestore(&emu->sflist->lock, sf_flags); } /* diff --git a/sound/synth/emux/soundfont.c b/sound/synth/emux/soundfont.c index eed47e4830248..0a788fe8bb8e0 100644 --- a/sound/synth/emux/soundfont.c +++ b/sound/synth/emux/soundfont.c @@ -1231,6 +1231,9 @@ delete_preset(struct snd_sf_list *sflist, struct snd_sf_zone *zp) * The found zones are stored on 'table' array. max_layers defines * the maximum number of elements in this array. * This function returns the number of found zones. 0 if not found. + * + * The caller must hold sflist->lock, and keep holding it as long as + * the returned zones are accessed. */ int snd_soundfont_search_zone(struct snd_sf_list *sflist, int *notep, int vel, @@ -1239,17 +1242,14 @@ snd_soundfont_search_zone(struct snd_sf_list *sflist, int *notep, int vel, struct snd_sf_zone **table, int max_layers) { int nvoices; - unsigned long flags; - /* this function is supposed to be called atomically, - * so we check the lock. if it's busy, just returns 0 to + lockdep_assert_held(&sflist->lock); + + /* if the presets are being modified, just returns 0 to * tell the caller the busy state */ - spin_lock_irqsave(&sflist->lock, flags); - if (sflist->presets_locked) { - spin_unlock_irqrestore(&sflist->lock, flags); + if (sflist->presets_locked) return 0; - } nvoices = search_zones(sflist, notep, vel, preset, bank, table, max_layers, 0); if (! nvoices) { @@ -1258,7 +1258,6 @@ snd_soundfont_search_zone(struct snd_sf_list *sflist, int *notep, int vel, def_preset, def_bank, table, max_layers, 0); } - spin_unlock_irqrestore(&sflist->lock, flags); return nvoices; } -- 2.53.0