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authorTejun Heo <tj@kernel.org>2008-09-03 16:09:47 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2008-09-03 19:58:53 -0700
commitce36394269ccd9d1d286d6192ba09fa6894365e9 (patch)
treefb235ff6ea1363ae4fd933e29268e76cdade5682 /mm/mmap.c
parentd210baf53b699fc61aa891c177b71d7082d3b957 (diff)
downloadlwn-ce36394269ccd9d1d286d6192ba09fa6894365e9.tar.gz
lwn-ce36394269ccd9d1d286d6192ba09fa6894365e9.zip
mmap: fix petty bug in anonymous shared mmap offset handling
Anonymous mappings should ignore offset but shared anonymous mapping forgot to clear it and makes the following legit test program trigger SIGBUS. #include <sys/mman.h> #include <stdio.h> #include <errno.h> #define PAGE_SIZE 4096 int main(void) { char *p; int i; p = mmap(NULL, 2 * PAGE_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, PAGE_SIZE); if (p == MAP_FAILED) { perror("mmap"); return 1; } for (i = 0; i < 2; i++) { printf("page %d\n", i); p[i * 4096] = i; } return 0; } Fix it. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Hugh Dickins <hugh@veritas.com> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 339cf5c4d5d8..e7a5a68a9c2e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1030,6 +1030,10 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
} else {
switch (flags & MAP_TYPE) {
case MAP_SHARED:
+ /*
+ * Ignore pgoff.
+ */
+ pgoff = 0;
vm_flags |= VM_SHARED | VM_MAYSHARE;
break;
case MAP_PRIVATE: