From: Aleksandr Nogikh <nogikh@xxxxxxxxxx> Subject: 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 (https://lkml.kernel.org/r/Ylkr2xrVbhQYwNLf@xxxxxxxxxxxxxxxx). 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/20220401182512.249282-1-nogikh@xxxxxxxxxx Fixes: b3d7fe86fbd0 ("kcov: properly handle subsequent mmap calls"), Signed-off-by: Aleksandr Nogikh <nogikh@xxxxxxxxxx> Acked-by: Marco Elver <elver@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Taras Madan <tarasmadan@xxxxxxxxxx> Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/kcov.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/kernel/kcov.c~kcov-dont-generate-a-warning-on-vm_insert_pages-failure +++ a/kernel/kcov.c @@ -475,8 +475,11 @@ static int kcov_mmap(struct file *filep, 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: _
