From: Andrew Morton <akpm@linux-foundation.org>
To: aarcange@redhat.com, akpm@linux-foundation.org,
axelrasmussen@google.com, dgilbert@redhat.com, joe@perches.com,
linux-mm@kvack.org, mm-commits@vger.kernel.org,
peterx@redhat.com, rppt@linux.vnet.ibm.com, shuah@kernel.org,
torvalds@linux-foundation.org
Subject: [patch 09/12] userfaultfd: selftests: fix SIGSEGV if huge mmap fails
Date: Sat, 05 Dec 2020 22:15:05 -0800 [thread overview]
Message-ID: <20201206061505.YYPXe9PBC%akpm@linux-foundation.org> (raw)
In-Reply-To: <20201205221412.67f14b9b3a5ef531c76dd452@linux-foundation.org>
From: Axel Rasmussen <axelrasmussen@google.com>
Subject: userfaultfd: selftests: fix SIGSEGV if huge mmap fails
The error handling in hugetlb_allocate_area() was incorrect for the
hugetlb_shared test case.
Previously the behavior was:
- mmap a hugetlb area
- If this fails, set the pointer to NULL, and carry on
- mmap an alias of the same hugetlb fd
- If this fails, munmap the original area
If the original mmap failed, it's likely the second one did too. If both
failed, we'd blindly try to munmap a NULL pointer, causing a SIGSEGV.
Instead, "goto fail" so we return before trying to mmap the alias.
This issue can be hit "in real life" by forgetting to set
/proc/sys/vm/nr_hugepages (leaving it at 0), and then trying to run the
hugetlb_shared test.
Another small improvement is, when the original mmap fails, don't just
print "it failed": perror(), so we can see *why*. :)
Link: https://lkml.kernel.org/r/20201204203443.2714693-1-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
tools/testing/selftests/vm/userfaultfd.c | 25 +++++++++++++--------
1 file changed, 16 insertions(+), 9 deletions(-)
--- a/tools/testing/selftests/vm/userfaultfd.c~userfaultfd-selftests-fix-sigsegv-if-huge-mmap-fails
+++ a/tools/testing/selftests/vm/userfaultfd.c
@@ -206,19 +206,19 @@ static int hugetlb_release_pages(char *r
return ret;
}
-
static void hugetlb_allocate_area(void **alloc_area)
{
void *area_alias = NULL;
char **alloc_area_alias;
+
*alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
(map_shared ? MAP_SHARED : MAP_PRIVATE) |
MAP_HUGETLB,
huge_fd, *alloc_area == area_src ? 0 :
nr_pages * page_size);
if (*alloc_area == MAP_FAILED) {
- fprintf(stderr, "mmap of hugetlbfs file failed\n");
- *alloc_area = NULL;
+ perror("mmap of hugetlbfs file failed");
+ goto fail;
}
if (map_shared) {
@@ -227,14 +227,11 @@ static void hugetlb_allocate_area(void *
huge_fd, *alloc_area == area_src ? 0 :
nr_pages * page_size);
if (area_alias == MAP_FAILED) {
- if (munmap(*alloc_area, nr_pages * page_size) < 0) {
- perror("hugetlb munmap");
- exit(1);
- }
- *alloc_area = NULL;
- return;
+ perror("mmap of hugetlb file alias failed");
+ goto fail_munmap;
}
}
+
if (*alloc_area == area_src) {
huge_fd_off0 = *alloc_area;
alloc_area_alias = &area_src_alias;
@@ -243,6 +240,16 @@ static void hugetlb_allocate_area(void *
}
if (area_alias)
*alloc_area_alias = area_alias;
+
+ return;
+
+fail_munmap:
+ if (munmap(*alloc_area, nr_pages * page_size) < 0) {
+ perror("hugetlb munmap");
+ exit(1);
+ }
+fail:
+ *alloc_area = NULL;
}
static void hugetlb_alias_mapping(__u64 *start, size_t len, unsigned long offset)
_
next prev parent reply other threads:[~2020-12-06 6:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-06 6:14 incoming Andrew Morton
2020-12-06 6:14 ` [patch 01/12] zlib: export S390 symbols for zlib modules Andrew Morton
2020-12-07 9:03 ` Zaslonko Mikhail
2020-12-08 0:45 ` Randy Dunlap
2020-12-08 8:19 ` Zaslonko Mikhail
2020-12-18 22:18 ` Randy Dunlap
2020-12-06 6:14 ` [patch 02/12] coredump: fix core_pattern parse error Andrew Morton
2020-12-06 6:14 ` [patch 03/12] mm: memcg/slab: fix obj_cgroup_charge() return value handling Andrew Morton
2020-12-06 6:14 ` [patch 04/12] mm: list_lru: set shrinker map bit when child nr_items is not zero Andrew Morton
2020-12-06 6:14 ` [patch 05/12] mm/zsmalloc.c: drop ZSMALLOC_PGTABLE_MAPPING Andrew Morton
2020-12-06 6:14 ` [patch 06/12] mm/swapfile: do not sleep with a spin lock held Andrew Morton
2020-12-06 6:14 ` [patch 07/12] mailmap: add two more addresses of Uwe Kleine-König Andrew Morton
2020-12-06 6:15 ` [patch 08/12] tools/testing/selftests/vm: fix build error Andrew Morton
2020-12-06 6:15 ` Andrew Morton [this message]
2020-12-06 6:15 ` [patch 10/12] mm/filemap: add static for function __add_to_page_cache_locked Andrew Morton
2020-12-06 6:15 ` [patch 11/12] hugetlb_cgroup: fix offline of hugetlb cgroup with reservations Andrew Morton
2020-12-06 6:15 ` [patch 12/12] mm/mmap.c: fix mmap return value when vma is merged after call_mmap() Andrew Morton
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