The patch titled
Subject: printk: guard the amount written per line by devkmsg_read()
has been added to the -mm tree. Its filename is
printk-guard-the-amount-written-per-line-by-devkmsg_read.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/printk-guard-the-amount-written-per-line-by-devkmsg_read.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/printk-guard-the-amount-written-per-line-by-devkmsg_read.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
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------------------------------------------------------
From: Tejun Heo <tj@xxxxxxxxxx>
Subject: printk: guard the amount written per line by devkmsg_read()
This patchset updates netconsole so that it can emit messages with the
same header as used in /dev/kmsg which gives neconsole receiver full
log information which enables things like structured logging and
detection of lost messages.
This patch (of 7):
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@xxxxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: Kay Sievers <kay@xxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/printk.h | 2 ++
kernel/printk/printk.c | 34 ++++++++++++++++++++++------------
2 files changed, 24 insertions(+), 12 deletions(-)
diff -puN include/linux/printk.h~printk-guard-the-amount-written-per-line-by-devkmsg_read include/linux/printk.h
--- a/include/linux/printk.h~printk-guard-the-amount-written-per-line-by-devkmsg_read
+++ a/include/linux/printk.h
@@ -30,6 +30,8 @@ static inline const char *printk_skip_le
return buffer;
}
+#define CONSOLE_EXT_LOG_MAX 8192
+
/* printk's without a loglevel use this.. */
#define MESSAGE_LOGLEVEL_DEFAULT CONFIG_MESSAGE_LOGLEVEL_DEFAULT
diff -puN kernel/printk/printk.c~printk-guard-the-amount-written-per-line-by-devkmsg_read kernel/printk/printk.c
--- a/kernel/printk/printk.c~printk-guard-the-amount-written-per-line-by-devkmsg_read
+++ a/kernel/printk/printk.c
@@ -505,6 +505,11 @@ int check_syslog_permissions(int type, b
return security_syslog(type);
}
+static void append_char(char **pp, char *e, char c)
+{
+ if (*pp < e)
+ *(*pp)++ = c;
+}
/* /dev/kmsg - userspace message inject/listen interface */
struct devkmsg_user {
@@ -512,7 +517,7 @@ 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)
@@ -570,6 +575,7 @@ static ssize_t devkmsg_read(struct file
{
struct devkmsg_user *user = file->private_data;
struct printk_log *msg;
+ char *p, *e;
u64 ts_usec;
size_t i;
char cont = '-';
@@ -579,6 +585,9 @@ static ssize_t devkmsg_read(struct file
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 +634,9 @@ static ssize_t devkmsg_read(struct file
((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 +644,11 @@ static ssize_t devkmsg_read(struct file
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 +657,31 @@ static ssize_t devkmsg_read(struct file
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;
_
Patches currently in -mm which might be from tj@xxxxxxxxxx are
origin.patch
gfp-add-__gfp_noaccount.patch
gfp-add-__gfp_noaccount-v2.patch
gfp-add-__gfp_noaccount-v2-fix.patch
kernfs-do-not-account-ino_ida-allocations-to-memcg.patch
block-restore-proc-partitions-to-not-display-non-partitionable-removable-devices.patch
fs-mpagec-forgotten-write_sync-in-case-of-data-integrity-write.patch
printk-guard-the-amount-written-per-line-by-devkmsg_read.patch
printk-factor-out-message-formatting-from-devkmsg_read.patch
printk-implement-support-for-extended-console-drivers.patch
netconsole-remove-unnecessary-netconsole_target_get-out-from-write_msg.patch
netconsole-make-netconsole_target-enabled-a-bool.patch
netconsole-make-all-dynamic-netconsoles-share-a-mutex.patch
netconsole-implement-extended-console-support.patch
bitmap-remove-explicit-newline-handling-using-scnprintf-format-string.patch
bitmap-remove-explicit-newline-handling-using-scnprintf-format-string-fix.patch
ipc-msgc-msgsnd-use-freezable-blocking-call.patch
msgrcv-use-freezable-blocking-call.patch
linux-next.patch
printk-improve-the-description-of-dev-kmsg-line-format.patch
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