• Nicolas Iooss's avatar
    eventpoll: fix uninitialized variable in epoll_ctl · c680e41b
    Nicolas Iooss authored
    When calling epoll_ctl with operation EPOLL_CTL_DEL, structure epds is
    not initialized but ep_take_care_of_epollwakeup reads its event field.
    When this unintialized field has EPOLLWAKEUP bit set, a capability check
    is done for CAP_BLOCK_SUSPEND in ep_take_care_of_epollwakeup.  This
    produces unexpected messages in the audit log, such as (on a system
    running SELinux):
    
        type=AVC msg=audit(1408212798.866:410): avc:  denied
        { block_suspend } for  pid=7754 comm="dbus-daemon" capability=36
        scontext=unconfined_u:unconfined_r:unconfined_t
        tcontext=unconfined_u:unconfined_r:unconfined_t
        tclass=capability2 permissive=1
    
        type=SYSCALL msg=audit(1408212798.866:410): arch=c000003e syscall=233
        success=yes exit=0 a0=3 a1=2 a2=9 a3=7fffd4d66ec0 items=0 ppid=1
        pid=7754 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0
        fsgid=0 tty=(none) ses=3 comm="dbus-daemon"
        exe="/usr/bin/dbus-daemon"
        subj=unconfined_u:unconfined_r:unconfined_t key=(null)
    
    ("arch=c000003e syscall=233 a1=2" means "epoll_ctl(op=EPOLL_CTL_DEL)")
    
    Remove use of epds in epoll_ctl when op == EPOLL_CTL_DEL.
    
    Fixes: 4d7e30d9 ("epoll: Add a flag, EPOLLWAKEUP, to prevent suspend while epoll events are ready")
    Signed-off-by: default avatarNicolas Iooss <nicolas.iooss_linux@m4x.org>
    Cc: Alexander Viro <viro@zeniv.linux.org.uk>
    Cc: Arve Hjønnevåg <arve@android.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    c680e41b
eventpoll.c 59 KB