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authorOleg Nesterov <oleg@redhat.com>2015-09-08 14:58:34 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-09-08 15:35:28 -0700
commitce75799b83aaf3fd592e21531a9532bed157c6b5 (patch)
treeae172990ba37e2985cb6b2c9fb833509390db7eb /mm/mmap.c
parent8a9cc3b55e9d20289cc18a65257e62c2dd4932fb (diff)
downloadlinux-ce75799b83aaf3fd592e21531a9532bed157c6b5.tar.bz2
mremap: fix the wrong !vma->vm_file check in copy_vma()
Test-case: #define _GNU_SOURCE #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> #include <assert.h> void *find_vdso_vaddr(void) { FILE *perl; char buf[32] = {}; perl = popen("perl -e 'open STDIN,qq|/proc/@{[getppid]}/maps|;" "/^(.*?)-.*vdso/ && print hex $1 while <>'", "r"); fread(buf, sizeof(buf), 1, perl); fclose(perl); return (void *)atol(buf); } #define PAGE_SIZE 4096 void *get_unmapped_area(void) { void *p = mmap(0, PAGE_SIZE, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1,0); assert(p != MAP_FAILED); munmap(p, PAGE_SIZE); return p; } char save[2][PAGE_SIZE]; int main(void) { void *vdso = find_vdso_vaddr(); void *page[2]; assert(vdso); memcpy(save, vdso, sizeof (save)); // force another fault on the next check assert(madvise(vdso, 2 * PAGE_SIZE, MADV_DONTNEED) == 0); page[0] = mremap(vdso, PAGE_SIZE, PAGE_SIZE, MREMAP_FIXED | MREMAP_MAYMOVE, get_unmapped_area()); page[1] = mremap(vdso + PAGE_SIZE, PAGE_SIZE, PAGE_SIZE, MREMAP_FIXED | MREMAP_MAYMOVE, get_unmapped_area()); assert(page[0] != MAP_FAILED && page[1] != MAP_FAILED); printf("match: %d %d\n", !memcmp(save[0], page[0], PAGE_SIZE), !memcmp(save[1], page[1], PAGE_SIZE)); return 0; } fails without this patch. Before the previous commit it gets the wrong page, now it segfaults (which is imho better). This is because copy_vma() wrongly assumes that if vma->vm_file == NULL is irrelevant until the first fault which will use do_anonymous_page(). This is obviously wrong for the special mapping. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 52b2f6e16f6f..52a2373d0ed4 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2918,7 +2918,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
* If anonymous vma has not yet been faulted, update new pgoff
* to match new location, to increase its chance of merging.
*/
- if (unlikely(!vma->vm_file && !vma->anon_vma)) {
+ if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
pgoff = addr >> PAGE_SHIFT;
faulted_in_anon_vma = false;
}