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Commit 7e5b58bc authored by Kay Sievers's avatar Kay Sievers Committed by Greg Kroah-Hartman
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printk: /dev/kmsg - properly support writev() to avoid interleaved printk() lines 



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: default avatarKay Sievers <kay.sievers@vrfy.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 47296b19

drivers/char/mem.c

+26 −15
Original line number Diff line number Diff line
@@ -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,

};