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authorJann Horn <jannh@google.com>2020-10-05 03:44:01 +0200
committerKees Cook <keescook@chromium.org>2020-10-08 13:17:47 -0700
commitdfe719fef03d752f1682fa8aeddf30ba501c8555 (patch)
tree7695a6683c814dbfd5174b10d55f51e071825bad /arch/microblaze
parent282a181b1a0d66de1f0894d82f395fcd478f51d1 (diff)
seccomp: Make duplicate listener detection non-racy
Currently, init_listener() tries to prevent adding a filter with SECCOMP_FILTER_FLAG_NEW_LISTENER if one of the existing filters already has a listener. However, this check happens without holding any lock that would prevent another thread from concurrently installing a new filter (potentially with a listener) on top of the ones we already have. Theoretically, this is also a data race: The plain load from current->seccomp.filter can race with concurrent writes to the same location. Fix it by moving the check into the region that holds the siglock to guard against concurrent TSYNC. (The "Fixes" tag points to the commit that introduced the theoretical data race; concurrent installation of another filter with TSYNC only became possible later, in commit 51891498f2da ("seccomp: allow TSYNC and USER_NOTIF together").) Fixes: 6a21cc50f0c7 ("seccomp: add a return code to trap to userspace") Reviewed-by: Tycho Andersen <tycho@tycho.pizza> Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Kees Cook <keescook@chromium.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201005014401.490175-1-jannh@google.com
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