From ae646f0b9ca135b87bc73ff606ef996c3029780a Mon Sep 17 00:00:00 2001 From: Jeffrey Hugo Date: Fri, 11 May 2018 16:01:42 -0700 Subject: init: fix false positives in W+X checking load_module() creates W+X mappings via __vmalloc_node_range() (from layout_and_allocate()->move_module()->module_alloc()) by using PAGE_KERNEL_EXEC. These mappings are later cleaned up via "call_rcu_sched(&freeinit->rcu, do_free_init)" from do_init_module(). This is a problem because call_rcu_sched() queues work, which can be run after debug_checkwx() is run, resulting in a race condition. If hit, the race results in a nasty splat about insecure W+X mappings, which results in a poor user experience as these are not the mappings that debug_checkwx() is intended to catch. This issue is observed on multiple arm64 platforms, and has been artificially triggered on an x86 platform. Address the race by flushing the queued work before running the arch-defined mark_rodata_ro() which then calls debug_checkwx(). Link: http://lkml.kernel.org/r/1525103946-29526-1-git-send-email-jhugo@codeaurora.org Fixes: e1a58320a38d ("x86/mm: Warn on W^X mappings") Signed-off-by: Jeffrey Hugo Reported-by: Timur Tabi Reported-by: Jan Glauber Acked-by: Kees Cook Acked-by: Ingo Molnar Acked-by: Will Deacon Acked-by: Laura Abbott Cc: Mark Rutland Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: Stephen Smalley Cc: Thomas Gleixner Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- init/main.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'init') diff --git a/init/main.c b/init/main.c index a404936d85d8..fd37315835b4 100644 --- a/init/main.c +++ b/init/main.c @@ -1034,6 +1034,13 @@ __setup("rodata=", set_debug_rodata); static void mark_readonly(void) { if (rodata_enabled) { + /* + * load_module() results in W+X mappings, which are cleaned up + * with call_rcu_sched(). Let's make sure that queued work is + * flushed so that we don't hit false positives looking for + * insecure pages which are W+X. + */ + rcu_barrier_sched(); mark_rodata_ro(); rodata_test(); } else -- cgit v1.2.3 From cd33d8803bfa3f5e6e5d7a4bb03fc8cc32c40fb6 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Tue, 15 May 2018 18:53:28 +0200 Subject: sched/fair: Fix documentation file path The 'tip' prefix probably referred to the -tip tree and is not required, remove it. Signed-off-by: Sebastian Andrzej Siewior Acked-by: Peter Zijlstra Cc: Linus Torvalds Cc: Paul Turner Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20180515165328.24899-1-bigeasy@linutronix.de Signed-off-by: Ingo Molnar --- init/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index f013afc74b11..18b151f0ddc1 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -738,7 +738,7 @@ config CFS_BANDWIDTH tasks running within the fair group scheduler. Groups with no limit set are considered to be unconstrained and will run with no restriction. - See tip/Documentation/scheduler/sched-bwc.txt for more information. + See Documentation/scheduler/sched-bwc.txt for more information. config RT_GROUP_SCHED bool "Group scheduling for SCHED_RR/FIFO" -- cgit v1.2.3