From: Petr Mladek <pmladek@suse.cz>
To: Tejun Heo <tj@kernel.org>
Cc: akpm@linux-foundation.org, davem@davemloft.net,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
Kay Sievers <kay@vrfy.org>
Subject: Re: [PATCH 01/16] printk: guard the amount written per line by devkmsg_read()
Date: Mon, 20 Apr 2015 14:11:36 +0200 [thread overview]
Message-ID: <20150420121136.GE4368@pathway.suse.cz> (raw)
In-Reply-To: <1429225433-11946-2-git-send-email-tj@kernel.org>
On Thu 2015-04-16 19:03:38, Tejun Heo wrote:
> devkmsg_read() uses 8k buffer and assumes that the formatted output
> message won't overrun which seems safe given LOG_LINE_MAX, the current
> use of dict and the escaping method being used; however, we're
> planning to use devkmsg formatting wider and accounting for the buffer
> size properly isn't that complicated.
>
> This patch defines CONSOLE_EXT_LOG_MAX as 8192 and updates
> devkmsg_read() so that it limits output accordingly.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
It is just a refactoring and does not modify the current behavior.
> Cc: Kay Sievers <kay@vrfy.org>
> Cc: Petr Mladek <pmladek@suse.cz>
> ---
> include/linux/printk.h | 2 ++
> kernel/printk/printk.c | 35 +++++++++++++++++++++++------------
> 2 files changed, 25 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/printk.h b/include/linux/printk.h
> index 9b30871..58b1fec 100644
> --- a/include/linux/printk.h
> +++ b/include/linux/printk.h
> @@ -30,6 +30,8 @@ static inline const char *printk_skip_level(const char *buffer)
> return buffer;
> }
>
> +#define CONSOLE_EXT_LOG_MAX 8192
If you do a respin from some reason. I would suggest to remove
"CONSOLE_" because it is used also for devkmsg.
Best Regards,
Petr
> +
> /* printk's without a loglevel use this.. */
> #define MESSAGE_LOGLEVEL_DEFAULT CONFIG_MESSAGE_LOGLEVEL_DEFAULT
>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 879edfc..b6e24af 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -512,7 +512,7 @@ struct devkmsg_user {
> u32 idx;
> enum log_flags prev;
> struct mutex lock;
> - char buf[8192];
> + char buf[CONSOLE_EXT_LOG_MAX];
> };
>
> static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
> @@ -565,11 +565,18 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
> return ret;
> }
>
> +static void append_char(char **pp, char *e, char c)
> +{
> + if (*pp < e)
> + *(*pp)++ = c;
> +}
> +
> static ssize_t devkmsg_read(struct file *file, char __user *buf,
> size_t count, loff_t *ppos)
> {
> struct devkmsg_user *user = file->private_data;
> struct printk_log *msg;
> + char *p, *e;
> u64 ts_usec;
> size_t i;
> char cont = '-';
> @@ -579,6 +586,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
> if (!user)
> return -EBADF;
>
> + p = user->buf;
> + e = user->buf + sizeof(user->buf);
> +
> ret = mutex_lock_interruptible(&user->lock);
> if (ret)
> return ret;
> @@ -625,9 +635,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
> ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
> cont = '+';
>
> - len = sprintf(user->buf, "%u,%llu,%llu,%c;",
> - (msg->facility << 3) | msg->level,
> - user->seq, ts_usec, cont);
> + p += scnprintf(p, e - p, "%u,%llu,%llu,%c;",
> + (msg->facility << 3) | msg->level,
> + user->seq, ts_usec, cont);
> user->prev = msg->flags;
>
> /* escape non-printable characters */
> @@ -635,11 +645,11 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
> unsigned char c = log_text(msg)[i];
>
> if (c < ' ' || c >= 127 || c == '\\')
> - len += sprintf(user->buf + len, "\\x%02x", c);
> + p += scnprintf(p, e - p, "\\x%02x", c);
> else
> - user->buf[len++] = c;
> + append_char(&p, e, c);
> }
> - user->buf[len++] = '\n';
> + append_char(&p, e, '\n');
>
> if (msg->dict_len) {
> bool line = true;
> @@ -648,30 +658,31 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
> unsigned char c = log_dict(msg)[i];
>
> if (line) {
> - user->buf[len++] = ' ';
> + append_char(&p, e, ' ');
> line = false;
> }
>
> if (c == '\0') {
> - user->buf[len++] = '\n';
> + append_char(&p, e, '\n');
> line = true;
> continue;
> }
>
> if (c < ' ' || c >= 127 || c == '\\') {
> - len += sprintf(user->buf + len, "\\x%02x", c);
> + p += scnprintf(p, e - p, "\\x%02x", c);
> continue;
> }
>
> - user->buf[len++] = c;
> + append_char(&p, e, c);
> }
> - user->buf[len++] = '\n';
> + append_char(&p, e, '\n');
> }
>
> user->idx = log_next(user->idx);
> user->seq++;
> raw_spin_unlock_irq(&logbuf_lock);
>
> + len = p - user->buf;
> if (len > count) {
> ret = -EINVAL;
> goto out;
> --
> 2.1.0
>
next prev parent reply other threads:[~2015-04-20 12:09 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-16 23:03 [PATCHSET] printk, netconsole: implement reliable netconsole Tejun Heo
2015-04-16 23:03 ` [PATCH 01/16] printk: guard the amount written per line by devkmsg_read() Tejun Heo
2015-04-20 12:11 ` Petr Mladek [this message]
2015-04-20 12:33 ` Petr Mladek
2015-04-16 23:03 ` [PATCH 02/16] printk: factor out message formatting from devkmsg_read() Tejun Heo
2015-04-20 12:30 ` Petr Mladek
2015-04-16 23:03 ` [PATCH 03/16] printk: move LOG_NOCONS skipping into call_console_drivers() Tejun Heo
2015-04-20 12:50 ` Petr Mladek
2015-04-16 23:03 ` [PATCH 04/16] printk: implement support for extended console drivers Tejun Heo
2015-04-20 15:43 ` Petr Mladek
2015-04-21 10:03 ` Petr Mladek
2015-04-27 21:09 ` Tejun Heo
2015-04-28 9:42 ` Petr Mladek
2015-04-28 14:10 ` Tejun Heo
2015-04-28 14:24 ` Petr Mladek
2015-04-16 23:03 ` [PATCH 05/16] printk: implement log_seq_range() and ext_log_from_seq() Tejun Heo
2015-04-16 23:03 ` [PATCH 06/16] netconsole: make netconsole_target->enabled a bool Tejun Heo
2015-04-16 23:03 ` [PATCH 07/16] netconsole: factor out alloc_netconsole_target() Tejun Heo
2015-04-16 23:03 ` [PATCH 08/16] netconsole: punt disabling to workqueue from netdevice_notifier Tejun Heo
2015-04-16 23:03 ` [PATCH 09/16] netconsole: replace target_list_lock with console_lock Tejun Heo
2015-04-16 23:03 ` [PATCH 10/16] netconsole: introduce netconsole_mutex Tejun Heo
2015-04-16 23:03 ` [PATCH 11/16] netconsole: consolidate enable/disable and create/destroy paths Tejun Heo
2015-04-16 23:03 ` [PATCH 12/16] netconsole: implement extended console support Tejun Heo
2015-04-16 23:03 ` [PATCH 13/16] netconsole: implement retransmission support for extended consoles Tejun Heo
2015-04-16 23:03 ` [PATCH 14/16] netconsole: implement ack handling and emergency transmission Tejun Heo
2015-04-16 23:03 ` [PATCH 15/16] netconsole: implement netconsole receiver library Tejun Heo
2015-04-16 23:03 ` [PATCH 16/16] netconsole: update documentation for extended netconsole Tejun Heo
2015-04-17 15:35 ` [PATCHSET] printk, netconsole: implement reliable netconsole Tetsuo Handa
2015-04-17 16:28 ` Tejun Heo
2015-04-17 17:17 ` David Miller
2015-04-17 17:37 ` Tejun Heo
2015-04-17 17:43 ` Tetsuo Handa
2015-04-17 17:45 ` Tejun Heo
2015-04-17 18:03 ` Tetsuo Handa
2015-04-17 18:07 ` Tejun Heo
2015-04-17 18:20 ` Tetsuo Handa
2015-04-17 18:26 ` Tejun Heo
2015-04-18 13:09 ` Tetsuo Handa
2015-04-17 18:04 ` Tejun Heo
2015-04-17 18:55 ` David Miller
2015-04-17 19:52 ` Tejun Heo
2015-04-17 20:06 ` David Miller
2015-04-21 21:51 ` Stephen Hemminger
2015-04-19 7:25 ` Rob Landley
2015-04-20 12:00 ` David Laight
2015-04-20 14:33 ` Tejun Heo
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