[PATCH] kmsg_write: don't return printk return value

kmsg_write returns with printk, so some programs may be confused by a
successful write() with a return value different than the buffer length.

# /bin/echo something > /dev/kmsg
/bin/echo: write error: Inappropriate ioctl for device

The drawbacks is that the printk return value can no more be quickly
checked from userspace.

Signed-off-by: Guillaume Chazarain <guichaz@yahoo.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 91dd669273e0..a85f3a361442 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -817,7 +817,7 @@ static ssize_t kmsg_write(struct file * file, const char __user * buf,
                           size_t count, loff_t *ppos)
 {
         char *tmp;
-        int ret;
+        ssize_t ret;
 
         tmp = kmalloc(count + 1, GFP_KERNEL);
         if (tmp == NULL)
@@ -826,6 +826,9 @@ static ssize_t kmsg_write(struct file * file, const char __user * buf,
         if (!copy_from_user(tmp, buf, count)) {
                 tmp[count] = 0;
                 ret = printk("%s", tmp);
+                if (ret > count)
+                        /* printk can add a prefix */
+                        ret = count;
         }
         kfree(tmp);
         return ret;