• Oleg Nesterov's avatar
    signal: remove the wrong signal_pending() check in restore_user_sigmask() · 97abc889
    Oleg Nesterov authored
    This is the minimal fix for stable, I'll send cleanups later.
    
    Commit 854a6ed5 ("signal: Add restore_user_sigmask()") introduced
    the visible change which breaks user-space: a signal temporary unblocked
    by set_user_sigmask() can be delivered even if the caller returns
    success or timeout.
    
    Change restore_user_sigmask() to accept the additional "interrupted"
    argument which should be used instead of signal_pending() check, and
    update the callers.
    
    Eric said:
    
    : For clarity.  I don't think this is required by posix, or fundamentally to
    : remove the races in select.  It is what linux has always done and we have
    : applications who care so I agree this fix is needed.
    :
    : Further in any case where the semantic change that this patch rolls back
    : (aka where allowing a signal to be delivered and the select like call to
    : complete) would be advantage we can do as well if not better by using
    : signalfd.
    :
    : Michael is there any chance we can get this guarantee of the linux
    : implementation of pselect and friends clearly documented.  The guarantee
    : that if the system call completes successfully we are guaranteed that no
    : signal that is unblocked by using sigmask will be delivered?
    
    Link: http://lkml.kernel.org/r/20190604134117.GA29963@redhat.com
    Fixes: 854a6ed5 ("signal: Add restore_user_sigmask()")
    Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
    Reported-by: default avatarEric Wong <e@80x24.org>
    Tested-by: default avatarEric Wong <e@80x24.org>
    Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
    Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
    Acked-by: default avatarDeepa Dinamani <deepa.kernel@gmail.com>
    Cc: Michael Kerrisk <mtk.manpages@gmail.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Davidlohr Bueso <dave@stgolabs.net>
    Cc: Jason Baron <jbaron@akamai.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Al Viro <viro@ZenIV.linux.org.uk>
    Cc: David Laight <David.Laight@ACULAB.COM>
    Cc: <stable@vger.kernel.org>	[5.0+]
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    97abc889
signal.c 115 KB