From 475f4dfc021c5fde69f3b7d3287bde0a50477b05 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Wed, 13 May 2020 17:50:41 -0700 Subject: mm/gup: fix fixup_user_fault() on multiple retries This part was overlooked when reworking the gup code on multiple retries. When we get the 2nd+ retry, we'll be with TRIED flag set. Current code will bail out on the 2nd retry because the !TRIED check will fail so the retry logic will be skipped. What's worse is that, it will also return zero which errornously hints the caller that the page is faulted in while it's not. The !TRIED flag check seems to not be needed even before the mutliple retries change because if we get a VM_FAULT_RETRY, it must be the 1st retry, and we should not have TRIED set for that. Fix it by removing the !TRIED check, at the meantime check against fatal signals properly before the page fault so we can still properly respond to the user killing the process during retries. Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times") Reported-by: Randy Dunlap Signed-off-by: Peter Xu Signed-off-by: Andrew Morton Cc: Alex Williamson Cc: Brian Geffon Link: http://lkml.kernel.org/r/20200502003523.8204-1-peterx@redhat.com Signed-off-by: Linus Torvalds --- mm/gup.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'mm') diff --git a/mm/gup.c b/mm/gup.c index 50681f0286de..87a6a59fe667 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1218,6 +1218,10 @@ retry: if (!vma_permits_fault(vma, fault_flags)) return -EFAULT; + if ((fault_flags & FAULT_FLAG_KILLABLE) && + fatal_signal_pending(current)) + return -EINTR; + ret = handle_mm_fault(vma, address, fault_flags); major |= ret & VM_FAULT_MAJOR; if (ret & VM_FAULT_ERROR) { @@ -1230,11 +1234,9 @@ retry: if (ret & VM_FAULT_RETRY) { down_read(&mm->mmap_sem); - if (!(fault_flags & FAULT_FLAG_TRIED)) { - *unlocked = true; - fault_flags |= FAULT_FLAG_TRIED; - goto retry; - } + *unlocked = true; + fault_flags |= FAULT_FLAG_TRIED; + goto retry; } if (tsk) { -- cgit