exec: pin stack limit during exec
Since the stack rlimit is used in multiple places during exec and it can be changed via other threads (via setrlimit()) or processes (via prlimit()), the assumption that the value doesn't change cannot be made. This leads to races with mm layout selection and argument size calculations. This changes the exec path to use the rlimit stored in bprm instead of in current. Before starting the thread, the bprm stack rlimit is stored back to current. Link: http://lkml.kernel.org/r/1518638796-20819-4-git-send-email-keescook@chromium.org Fixes: 64701dee ("exec: Use sane stack rlimit under secureexec") Signed-off-by: NKees Cook <keescook@chromium.org> Reported-by: NBen Hutchings <ben.hutchings@codethink.co.uk> Reported-by: NAndy Lutomirski <luto@kernel.org> Reported-by: NBrad Spengler <spender@grsecurity.net> Acked-by: NMichal Hocko <mhocko@suse.com> Cc: Ben Hutchings <ben@decadent.org.uk> Cc: Greg KH <greg@kroah.com> Cc: Hugh Dickins <hughd@google.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Laura Abbott <labbott@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Willy Tarreau <w@1wt.eu> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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