From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <48BE9AAB.9070303@kernel.org> Date: Wed, 03 Sep 2008 16:09:47 +0200 From: Tejun Heo MIME-Version: 1.0 Subject: [PATCH #2.6.27-rc5] mmap: fix petty bug in anonymous shared mmap offset handling Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: linux-mm@kvack.org, Linux Kernel Mailing List , Linus Torvalds List-ID: Anonymous mappings should ignore offset but shared anonymous mapping forgot to clear it and makes the following legit test program trigger SIGBUS. #include #include #include #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 --- mm/mmap.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/mmap.c b/mm/mmap.c index 339cf5c..e7a5a68 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: -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org