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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: Kay Sievers <kay.sievers@vrfy.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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parent
47296b1962
commit
7e5b58bcbc
1 changed files with 26 additions and 15 deletions
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@ -806,29 +806,40 @@ static const struct file_operations oldmem_fops = {
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};
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#endif
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static ssize_t kmsg_write(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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static ssize_t kmsg_writev(struct kiocb *iocb, const struct iovec *iv,
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unsigned long count, loff_t pos)
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{
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char *tmp;
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ssize_t ret;
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char *line, *p;
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int len, i;
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ssize_t ret = -EFAULT;
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tmp = kmalloc(count + 1, GFP_KERNEL);
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if (tmp == NULL)
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len = iov_length(iv, count);
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line = p = kmalloc(len + 1, GFP_KERNEL);
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if (line == NULL)
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return -ENOMEM;
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ret = -EFAULT;
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if (!copy_from_user(tmp, buf, count)) {
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tmp[count] = 0;
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ret = printk("%s", tmp);
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if (ret > count)
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/* printk can add a prefix */
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ret = count;
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/*
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* copy all vectors into a single string, to ensure we do
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* not interleave our log line with other printk calls
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*/
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for (i = 0; i < count; i++) {
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if (copy_from_user(p, iv[i].iov_base, iv[i].iov_len))
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goto out;
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p += iv[i].iov_len;
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}
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kfree(tmp);
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p[0] = '\0';
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ret = printk("%s", line);
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/* printk can add a prefix */
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if (ret > len)
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ret = len;
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out:
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kfree(line);
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return ret;
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}
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static const struct file_operations kmsg_fops = {
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.write = kmsg_write,
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.aio_write = kmsg_writev,
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.llseek = noop_llseek,
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};
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