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authorSiddhesh Poyarekar <siddhesh.poyarekar@gmail.com>2012-05-29 15:06:22 -0700
committerBen Hutchings <ben@decadent.org.uk>2012-06-10 14:41:44 +0100
commitff8445f52037e30411691d0d1ced9650c780c3c2 (patch)
treeef08d7aecd8f2936b3221af908bcd3c3fa27685c /kernel
parenta3a704a9ab01cf1f65df997868ddeb611e244dfb (diff)
mm/fork: fix overflow in vma length when copying mmap on clone
commit 7edc8b0ac16cbaed7cb4ea4c6b95ce98d2997e84 upstream. The vma length in dup_mmap is calculated and stored in a unsigned int, which is insufficient and hence overflows for very large maps (beyond 16TB). The following program demonstrates this: #include <stdio.h> #include <unistd.h> #include <sys/mman.h> #define GIG 1024 * 1024 * 1024L #define EXTENT 16393 int main(void) { int i, r; void *m; char buf[1024]; for (i = 0; i < EXTENT; i++) { m = mmap(NULL, (size_t) 1 * 1024 * 1024 * 1024L, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0); if (m == (void *)-1) printf("MMAP Failed: %d\n", m); else printf("%d : MMAP returned %p\n", i, m); r = fork(); if (r == 0) { printf("%d: successed\n", i); return 0; } else if (r < 0) printf("FORK Failed: %d\n", r); else if (r > 0) wait(NULL); } return 0; } Increase the storage size of the result to unsigned long, which is sufficient for storing the difference between addresses. Signed-off-by: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com> Cc: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/fork.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 26f1ab0b1c95..79ee71f8b5a0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -352,7 +352,8 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
}
charge = 0;
if (mpnt->vm_flags & VM_ACCOUNT) {
- unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
+ unsigned long len;
+ len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
if (security_vm_enough_memory(len))
goto fail_nomem;
charge = len;