eventpoll: propagate wakeup source creation failure in ep_modify()

When EPOLL_CTL_MOD adds EPOLLWAKEUP, ep_modify() ignores the return
value of ep_create_wakeup_source(). If allocation fails, it returns
success with EPOLLWAKEUP set but no per-item wakeup source, so the
requested suspend protection is missing.

This can happen without fault injection on SELinux systems: creating
the wakeup source's sysfs nodes can require GFP_KERNEL_ACCOUNT
allocations for security.selinux xattrs, which can fail when the
caller's memory cgroup is over its limit.

Create the wakeup source before updating the event mask and data, and
return the error if creation fails. Leave any newly created per-epoll
source in place until ep_free(), as ep_insert() does on failure.

Fixes: 4d7e30d98939 ("epoll: Add a flag, EPOLLWAKEUP, to prevent suspend while epoll events are ready")
Signed-off-by: Tianyi Chen <hi@tychen.cc>
Link: https://patch.msgid.link/179240281988.1700986.8309527041821666235@tychen.cc
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

0 files changed, 0 insertions, 0 deletions