From ecc04463d1a36f88baa750d45dfb02c364e1fdb1 Mon Sep 17 00:00:00 2001 From: Aleksandr Nogikh Date: Thu, 21 Apr 2022 16:36:07 -0700 Subject: [PATCH] kcov: don't generate a warning on vm_insert_page()'s failure vm_insert_page()'s failure is not an unexpected condition, so don't do WARN_ONCE() in such a case. Instead, print a kernel message and just return an error code. This flaw has been reported under an OOM condition by sysbot [1]. The message is mainly for the benefit of the test log, in this case the fuzzer's log so that humans inspecting the log can figure out what was going on. KCOV is a testing tool, so I think being a little more chatty when KCOV unexpectedly is about to fail will save someone debugging time. We don't want the WARN, because it's not a kernel bug that syzbot should report, and failure can happen if the fuzzer tries hard enough (as above). Link: https://lkml.kernel.org/r/Ylkr2xrVbhQYwNLf@elver.google.com [1] Link: https://lkml.kernel.org/r/20220401182512.249282-1-nogikh@google.com Fixes: b3d7fe86fbd0 ("kcov: properly handle subsequent mmap calls"), Signed-off-by: Aleksandr Nogikh Acked-by: Marco Elver Cc: Dmitry Vyukov Cc: Andrey Konovalov Cc: Alexander Potapenko Cc: Taras Madan Cc: Sebastian Andrzej Siewior Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/kcov.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/kcov.c b/kernel/kcov.c index 475524bd900a..b3732b210593 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -475,8 +475,11 @@ static int kcov_mmap(struct file *filep, struct vm_area_struct *vma) vma->vm_flags |= VM_DONTEXPAND; for (off = 0; off < size; off += PAGE_SIZE) { page = vmalloc_to_page(kcov->area + off); - if (vm_insert_page(vma, vma->vm_start + off, page)) - WARN_ONCE(1, "vm_insert_page() failed"); + res = vm_insert_page(vma, vma->vm_start + off, page); + if (res) { + pr_warn_once("kcov: vm_insert_page() failed\n"); + return res; + } } return 0; exit: