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printk: /dev/kmsg - properly support writev() to avoid interleaved printk() lines

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printk: /dev/kmsg - properly support writev() to avoid interleaved printk lines

We should avoid calling printk() in a loop, when we pass a single
string to /dev/kmsg with writev().

Cc: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Kay Sievers 2011-04-07 04:29:20 +02:00 committed by Greg Kroah-Hartman
parent 47296b1962
commit 7e5b58bcbc
1 changed files with 26 additions and 15 deletions
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41
drivers/char/mem.c
View file

@ -806,29 +806,40 @@ static const struct file_operations oldmem_fops = {
};
#endif
static ssize_t kmsg_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
static ssize_t kmsg_writev(struct kiocb *iocb, const struct iovec *iv,
unsigned long count, loff_t pos)
{
char *tmp;
ssize_t ret;
char *line, *p;
int len, i;
ssize_t ret = -EFAULT;
tmp = kmalloc(count + 1, GFP_KERNEL);
if (tmp == NULL)
len = iov_length(iv, count);
line = p = kmalloc(len + 1, GFP_KERNEL);
if (line == NULL)
return -ENOMEM;
ret = -EFAULT;
if (!copy_from_user(tmp, buf, count)) {
tmp[count] = 0;
ret = printk("%s", tmp);
if (ret > count)
/* printk can add a prefix */
ret = count;
/*
* copy all vectors into a single string, to ensure we do
* not interleave our log line with other printk calls
*/
for (i = 0; i < count; i++) {
if (copy_from_user(p, iv[i].iov_base, iv[i].iov_len))
goto out;
p += iv[i].iov_len;
}
kfree(tmp);
p[0] = '\0';
ret = printk("%s", line);
/* printk can add a prefix */
if (ret > len)
ret = len;
out:
kfree(line);
return ret;
}
static const struct file_operations kmsg_fops = {
.write = kmsg_write,
.aio_write = kmsg_writev,
.llseek = noop_llseek,
};