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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, hirofumi@mail.parknet.co.jp,
	linux-mm@kvack.org, mm-commits@vger.kernel.org,
	stable@vger.kernel.org, torvalds@linux-foundation.org,
	willy@infradead.org
Subject: [patch 11/29] mm/highmem.c: fix zero_user_segments() with start > end
Date: Fri, 12 Mar 2021 21:07:37 -0800	[thread overview]
Message-ID: <20210313050737.mOQhR0vUf%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210312210632.9b7d62973d72a56fb13c7a03@linux-foundation.org>

From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Subject: mm/highmem.c: fix zero_user_segments() with start > end

zero_user_segments() is used from __block_write_begin_int(), for example
like the following

	zero_user_segments(page, 4096, 1024, 512, 918)

But new the zero_user_segments() implementation for for HIGHMEM +
TRANSPARENT_HUGEPAGE doesn't handle "start > end" case correctly, and hits
BUG_ON().  (we can fix __block_write_begin_int() instead though, it is the
old and multiple usage)

Also it calls kmap_atomic() unnecessarily while start == end == 0.

Link: https://lkml.kernel.org/r/87v9ab60r4.fsf@mail.parknet.co.jp
Fixes: 0060ef3b4e6d ("mm: support THPs in zero_user_segments")
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/highmem.c |   17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

--- a/mm/highmem.c~fix-zero_user_segments-with-start-end
+++ a/mm/highmem.c
@@ -368,20 +368,24 @@ void zero_user_segments(struct page *pag
 
 	BUG_ON(end1 > page_size(page) || end2 > page_size(page));
 
+	if (start1 >= end1)
+		start1 = end1 = 0;
+	if (start2 >= end2)
+		start2 = end2 = 0;
+
 	for (i = 0; i < compound_nr(page); i++) {
 		void *kaddr = NULL;
 
-		if (start1 < PAGE_SIZE || start2 < PAGE_SIZE)
-			kaddr = kmap_atomic(page + i);
-
 		if (start1 >= PAGE_SIZE) {
 			start1 -= PAGE_SIZE;
 			end1 -= PAGE_SIZE;
 		} else {
 			unsigned this_end = min_t(unsigned, end1, PAGE_SIZE);
 
-			if (end1 > start1)
+			if (end1 > start1) {
+				kaddr = kmap_atomic(page + i);
 				memset(kaddr + start1, 0, this_end - start1);
+			}
 			end1 -= this_end;
 			start1 = 0;
 		}
@@ -392,8 +396,11 @@ void zero_user_segments(struct page *pag
 		} else {
 			unsigned this_end = min_t(unsigned, end2, PAGE_SIZE);
 
-			if (end2 > start2)
+			if (end2 > start2) {
+				if (!kaddr)
+					kaddr = kmap_atomic(page + i);
 				memset(kaddr + start2, 0, this_end - start2);
+			}
 			end2 -= this_end;
 			start2 = 0;
 		}
_

  parent reply	other threads:[~2021-03-13  5:08 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-13  5:06 incoming Andrew Morton
2021-03-13  5:07 ` [patch 01/29] memblock: fix section mismatch warning Andrew Morton
2021-03-13  5:07 ` [patch 02/29] stop_machine: mark helpers __always_inline Andrew Morton
2021-03-13  5:07 ` [patch 03/29] init/Kconfig: make COMPILE_TEST depend on HAS_IOMEM Andrew Morton
2021-03-13  5:07 ` [patch 04/29] mm/page_alloc.c: refactor initialization of struct page for holes in memory layout Andrew Morton
2021-03-13  5:07 ` [patch 05/29] mm/fork: clear PASID for new mm Andrew Morton
2021-03-13  5:07 ` [patch 06/29] hugetlb: dedup the code to add a new file_region Andrew Morton
2021-03-13  5:07 ` [patch 07/29] hugetlb: break earlier in add_reservation_in_range() when we can Andrew Morton
2021-03-13  5:07 ` [patch 08/29] mm: introduce page_needs_cow_for_dma() for deciding whether cow Andrew Morton
2021-03-13  5:07 ` [patch 09/29] mm: use is_cow_mapping() across tree where proper Andrew Morton
2021-03-13  5:07 ` [patch 10/29] hugetlb: do early cow when page pinned on src mm Andrew Morton
2021-03-13  5:07 ` Andrew Morton [this message]
2021-03-13  5:07 ` [patch 12/29] binfmt_misc: fix possible deadlock in bm_register_write Andrew Morton
2021-03-13  5:07 ` [patch 13/29] MAINTAINERS: exclude uapi directories in API/ABI section Andrew Morton
2021-03-13  5:07 ` [patch 14/29] linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP* Andrew Morton
2021-03-13  5:07 ` [patch 15/29] kfence: fix printk format for ptrdiff_t Andrew Morton
2021-03-13  5:07 ` [patch 16/29] kfence, slab: fix cache_alloc_debugcheck_after() for bulk allocations Andrew Morton
2021-03-13  5:08 ` [patch 17/29] kfence: fix reports if constant function prefixes exist Andrew Morton
2021-03-13  5:08 ` [patch 18/29] include/linux/sched/mm.h: use rcu_dereference in in_vfork() Andrew Morton
2021-03-13  5:08 ` [patch 19/29] mm/madvise: replace ptrace attach requirement for process_madvise Andrew Morton
2021-03-13  5:08 ` [patch 20/29] kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC Andrew Morton
2021-03-13  5:08 ` [patch 21/29] kasan: fix KASAN_STACK dependency for HW_TAGS Andrew Morton
2021-03-13  5:08 ` [patch 22/29] mm/userfaultfd: fix memory corruption due to writeprotect Andrew Morton
2021-03-13  5:08 ` [patch 23/29] mm, hwpoison: do not lock page again when me_huge_page() successfully recovers Andrew Morton
2021-03-13 19:23   ` Linus Torvalds
2021-03-14  6:36     ` HORIGUCHI NAOYA(堀口　直也)
2021-03-13  5:08 ` [patch 24/29] ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls Andrew Morton
2021-03-13  5:08 ` [patch 25/29] ia64: fix ptrace(PTRACE_SYSCALL_INFO_EXIT) sign Andrew Morton
2021-03-13  5:08 ` [patch 26/29] mm/memcg: rename mem_cgroup_split_huge_fixup to split_page_memcg and add nr_pages argument Andrew Morton
2021-03-13  5:08 ` [patch 27/29] mm/memcg: set memcg when splitting page Andrew Morton
2021-03-13  5:08 ` [patch 28/29] zram: fix return value on writeback_store Andrew Morton
2021-03-13  5:08 ` [patch 29/29] zram: fix broken page writeback Andrew Morton

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