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[34.104.240.5]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc756a18dd0sm1274902a12.5.2026.09.22.10.02.45 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 22 Sep 2026 10:02:47 -0700 (PDT) From: Ginger Li To: jirislaby@kernel.org, gregkh@linuxfoundation.org Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Maarten.Brock@sttls.nl Subject: [PATCH v2] serial: max3100: Fix a data race on s->rts in max3100_work() Date: Wed, 23 Sep 2026 01:02:39 +0800 Message-ID: <20260922170239.33485-1-ginger.jzllee@gmail.com> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20260922053151.11260-1-ginger.jzllee@gmail.com> References: <20260922053151.11260-1-ginger.jzllee@gmail.com> Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit max3100_set_mctrl() stores the new RTS state and raises s->rts_commit to tell max3100_work() that it has to program it: spin_lock(&s->conf_lock); if (s->rts != rts) { s->rts = rts; s->rts_commit = 1; } if (s->loopback_commit || s->rts_commit) max3100_dowork(s); spin_unlock(&s->conf_lock); max3100_work() consumes s->rts_commit under s->conf_lock, but reads s->rts itself outside of the lock, both when it services that pending update and when it later transmits a character, so the state it programs into the hardware can be stale. Read s->rts into a local variable in the s->conf_lock protected snapshot at the top of the loop, before s->rts_commit is consumed, in the same way as s->conf is read before s->conf_commit. Fixes: 7831d56b0a35 ("tty: MAX3100") Signed-off-by: Ginger Li --- v2: - read s->rts into "rts" before s->rts_commit is consumed, as suggested by Maarten - mention s->rts_commit in the commit message - left the s->rts / s->rts_commit split alone; folding both into one byte would be a separate cleanup --- drivers/tty/serial/max3100.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/max3100.c b/drivers/tty/serial/max3100.c --- a/drivers/tty/serial/max3100.c +++ b/drivers/tty/serial/max3100.c @@ -236,6 +236,7 @@ static void max3100_work(struct work_struct *w) struct tty_port *tport = &s->port.state->port; unsigned char ch; int conf, cconf, cloopback, crts; + bool rts; int rxchars; u16 tx, rx; @@ -249,6 +250,7 @@ static void max3100_work(struct work_struct *w) s->conf_commit = 0; cloopback = s->loopback_commit; s->loopback_commit = 0; + rts = s->rts; crts = s->rts_commit; s->rts_commit = 0; spin_unlock(&s->conf_lock); @@ -258,7 +260,7 @@ static void max3100_work(struct work_struct *w) max3100_sr(s, 0x4001, &rx); if (crts) { max3100_sr(s, MAX3100_WD | MAX3100_TE | - (s->rts ? MAX3100_RTS : 0), &rx); + (rts ? MAX3100_RTS : 0), &rx); rxchars += max3100_handlerx(s, rx); } @@ -277,7 +279,7 @@ static void max3100_work(struct work_struct *w) } if (tx != 0xffff) { max3100_calc_parity(s, &tx); - tx |= MAX3100_WD | (s->rts ? MAX3100_RTS : 0); + tx |= MAX3100_WD | (rts ? MAX3100_RTS : 0); max3100_sr(s, tx, &rx); rxchars += max3100_handlerx(s, rx); } -- 2.43.0