From: Jiri Slaby <jirislaby@kernel.org>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
John Ogness <john.ogness@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] tty: use printk_safe context at tty_msg()
Date: Tue, 6 Apr 2021 06:51:37 +0200 [thread overview]
Message-ID: <a7f5103f-0912-30e1-611c-36c18a1eefd6@kernel.org> (raw)
In-Reply-To: <20210403041444.4081-1-penguin-kernel@I-love.SAKURA.ne.jp>
On 03. 04. 21, 6:14, Tetsuo Handa wrote:
> syzbot is reporting circular locking dependency due to calling printk()
> with port lock held [1]. When this problem was reported, we worried
> whether printk_safe context will remain available in future kernels [2],
> and then this problem was forgotten. But in order to utilize syzbot's
> resource for finding other bugs/reproducers by closing this one of top
> crashers, let's apply a patch which counts on availability of printk_safe
> context.
>
> syzbot is also reporting same dependency due to memory allocation fault
> injection at tty_buffer_alloc(). Although __GFP_NOWARN cannot prevent
> memory allocation fault injection from calling printk(), let's use
> __GFP_NOWARN at tty_buffer_alloc() in addition to using printk_safe
> context, for generating many lines of messages due to warn_alloc() is
> annoying. If we want to report it, we can use pr_warn() instead.
>
> [1] https://syzkaller.appspot.com/bug?id=39ea6caa479af471183997376dc7e90bc7d64a6a
> [2] https://lkml.kernel.org/r/20190218054649.GA26686@jagdpanzerIV
>
> Reported-by: syzbot <syzbot+43e93968b964e369db0b@syzkaller.appspotmail.com>
> Reported-by: syzbot <syzbot+3ed715090790806d8b18@syzkaller.appspotmail.com>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Fixes: b6da31b2c07c46f2 ("tty: Fix data race in tty_insert_flip_string_fixed_flag")
> Cc: <stable@vger.kernel.org> # 4.18+
> ---
> drivers/tty/tty_buffer.c | 5 ++++-
> include/linux/tty.h | 9 ++++++++-
> 2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
> index 6d4995a5f318..d59f7873bc49 100644
> --- a/drivers/tty/tty_buffer.c
> +++ b/drivers/tty/tty_buffer.c
> @@ -156,6 +156,7 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
> {
> struct llist_node *free;
> struct tty_buffer *p;
> + unsigned long flags;
>
> /* Round the buffer size out */
> size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
> @@ -172,7 +173,9 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
> have queued and recycle that ? */
> if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
> return NULL;
> - p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
> + printk_safe_enter_irqsave(flags);
> + p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC | __GFP_NOWARN);
> + printk_safe_exit_irqrestore(flags);
> if (p == NULL)
> return NULL;
>
> diff --git a/include/linux/tty.h b/include/linux/tty.h
> index 95fc2f100f12..7ae8eb46fec3 100644
> --- a/include/linux/tty.h
> +++ b/include/linux/tty.h
> @@ -14,6 +14,7 @@
> #include <uapi/linux/tty.h>
> #include <linux/rwsem.h>
> #include <linux/llist.h>
> +#include <../../kernel/printk/internal.h>
Including printk's internal header in linux/tty.h doesn't look correct
to me.
> @@ -773,7 +774,13 @@ static inline void proc_tty_unregister_driver(struct tty_driver *d) {}
> #endif
>
> #define tty_msg(fn, tty, f, ...) \
> - fn("%s %s: " f, tty_driver_name(tty), tty_name(tty), ##__VA_ARGS__)
> + do { \
> + unsigned long flags; \
> + \
> + printk_safe_enter_irqsave(flags); \
> + fn("%s %s: " f, tty_driver_name(tty), tty_name(tty), ##__VA_ARGS__); \
> + printk_safe_exit_irqrestore(flags); \
> + } while (0)
>
> #define tty_debug(tty, f, ...) tty_msg(pr_debug, tty, f, ##__VA_ARGS__)
> #define tty_info(tty, f, ...) tty_msg(pr_info, tty, f, ##__VA_ARGS__)
>
--
js
next prev parent reply other threads:[~2021-04-06 4:51 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-03 4:14 [PATCH] tty: use printk_safe context at tty_msg() Tetsuo Handa
2021-04-03 6:52 ` kernel test robot
2021-04-03 10:11 ` [PATCH] printk: Make multiple inclusion of kernel/printk/internal.h safe Tetsuo Handa
2021-04-06 4:51 ` Jiri Slaby [this message]
2021-04-06 5:31 ` [PATCH] tty: use printk_safe context at tty_msg() Tetsuo Handa
2021-04-06 7:10 ` Greg Kroah-Hartman
2021-04-06 11:16 ` Tetsuo Handa
2021-04-06 13:42 ` Greg Kroah-Hartman
2021-04-06 15:10 ` Petr Mladek
2021-04-06 16:22 ` Tetsuo Handa
2021-04-06 19:10 ` Greg Kroah-Hartman
2021-04-07 9:20 ` Petr Mladek
2021-04-07 13:26 ` [PATCH v2] tty: use printk_deferred() " Tetsuo Handa
2021-04-07 13:48 ` Greg Kroah-Hartman
2021-04-07 14:24 ` Tetsuo Handa
2021-04-12 10:39 ` How to handle concurrent access to /dev/ttyprintk ? Tetsuo Handa
2021-04-12 10:44 ` Greg Kroah-Hartman
2021-04-12 11:25 ` Tetsuo Handa
2021-04-12 12:04 ` Greg Kroah-Hartman
2021-04-14 0:45 ` Tetsuo Handa
2021-04-14 11:11 ` Tetsuo Handa
2021-04-14 16:15 ` Samo Pogačnik
2021-04-15 0:22 ` [PATCH] ttyprintk: Add TTY hangup callback Tetsuo Handa
2021-04-18 11:16 ` Samo Pogačnik
2021-04-22 10:02 ` Greg Kroah-Hartman
2021-04-23 4:22 ` Jiri Slaby
2021-04-23 9:55 ` Samo Pogačnik
2021-04-23 10:12 ` Tetsuo Handa
2021-04-23 19:47 ` Samo Pogačnik
2021-04-24 1:16 ` Tetsuo Handa
2021-04-24 9:57 ` Samo Pogačnik
2021-04-26 10:00 ` Petr Mladek
2021-04-26 16:42 ` Samo Pogačnik
2021-04-27 10:08 ` Petr Mladek
2021-04-27 11:31 ` Samo Pogačnik
2021-04-23 10:28 ` Jiri Slaby
2021-04-23 12:23 ` [PATCH] ttyprintk: Add TTY port shutdown callback Samo Pogačnik
2021-04-12 12:41 ` How to handle concurrent access to /dev/ttyprintk ? Samo Pogačnik
2021-04-13 9:41 ` Petr Mladek
2021-04-13 11:10 ` Samo Pogačnik
2021-04-13 14:32 ` Petr Mladek
2021-04-13 15:22 ` Samo Pogačnik
2021-04-14 17:36 ` Petr Mladek
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