[tip:timers/urgent] posix-clock: Fix return code on the poll method's error path

[tip-bot for Richard Cochran]

Commit-ID:  1b9f23727abb92c5e58f139e7d180befcaa06fe0
Gitweb:     http://git.kernel.org/tip/1b9f23727abb92c5e58f139e7d180befcaa06fe0
Author:     Richard Cochran <richardcochran@xxxxxxxxx>
AuthorDate: Tue, 22 Dec 2015 22:19:58 +0100
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 29 Dec 2015 11:33:06 +0100

posix-clock: Fix return code on the poll method's error path

The posix_clock_poll function is supposed to return a bit mask of
POLLxxx values.  However, in case the hardware has disappeared (due to
hot plugging for example) this code returns -ENODEV in a futile
attempt to throw an error at the file descriptor level.  The kernel's
file_operations interface does not accept such error codes from the
poll method.  Instead, this function aught to return POLLERR.

The value -ENODEV does, in fact, contain the POLLERR bit (and almost
all the other POLLxxx bits as well), but only by chance.  This patch
fixes code to return a proper bit mask.

Credit goes to Markus Elfring for pointing out the suspicious
signed/unsigned mismatch.

Reported-by: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
igned-off-by: Richard Cochran <richardcochran@xxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Julia Lawall <julia.lawall@xxxxxxx>
Link: http://lkml.kernel.org/r/1450819198-17420-1-git-send-email-richardcochran@xxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 kernel/time/posix-clock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c
index ce033c7..9cff0ab 100644
--- a/kernel/time/posix-clock.c
+++ b/kernel/time/posix-clock.c
@@ -69,10 +69,10 @@ static ssize_t posix_clock_read(struct file *fp, char __user *buf,
 static unsigned int posix_clock_poll(struct file *fp, poll_table *wait)
 {
 	struct posix_clock *clk = get_posix_clock(fp);
-	int result = 0;
+	unsigned int result = 0;
 
 	if (!clk)
-		return -ENODEV;
+		return POLLERR;
 
 	if (clk->ops.poll)
 		result = clk->ops.poll(clk, fp, wait);
--
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