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epoll: Fix user space breakage related to EPOLLWAKEUP

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Commit 4d7e30d (epoll: Add a flag, EPOLLWAKEUP, to prevent
suspend while epoll events are ready) caused some applications to
malfunction, because they set the bit corresponding to the new
EPOLLWAKEUP flag in their eventpoll flags and they don't have the
new CAP_EPOLLWAKEUP capability.

To prevent that from happening, change epoll_ctl() to clear
EPOLLWAKEUP in epds.events if the caller doesn't have the
CAP_EPOLLWAKEUP capability instead of failing and returning an
error code, which allows the affected applications to function
normally.

Reported-and-tested-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
This commit is contained in:
Rafael J. Wysocki
2012-05-21 21:20:48 +02:00
committed by Andy Whitcroft
parent 815745edaa
commit 7cde3ea5f1
1 changed files with 1 additions and 1 deletions
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2
fs/eventpoll.c
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@@ -1713,7 +1713,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
/* Check if EPOLLWAKEUP is allowed */
if ((epds.events & EPOLLWAKEUP) && !capable(CAP_EPOLLWAKEUP))
goto error_tgt_fput;
epds.events &= ~EPOLLWAKEUP;
/*
* We have to check that the file structure underneath the file descriptor