Re: [PATCH] fix double unlock_page() in 2.6.26-rc5-mm3 kernel BUGat mm/filemap.c:575!

[Kamalesh Babulal]

KAMEZAWA Hiroyuki wrote:
> This is reproducer of panic. "quick fix" is attached.
> But I think putback_lru_page() should be re-designed.
> 
> ==
> #include <stdio.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <sys/mman.h>
> #include <unistd.h>
> #include <errno.h>
> 
> int main(int argc, char *argv[])
> {
>         int fd;
>         char *filename = argv[1];
>         char buffer[4096];
>         char *addr;
>         int len;
> 
>         fd = open(filename, O_CREAT | O_EXCL | O_RDWR, S_IRWXU);
> 
>         if (fd < 0) {
>                 perror("open");
>                 exit(1);
>         }
>         len = write(fd, buffer, sizeof(buffer));
> 
>         if (len < 0) {
>                 perror("write");
>                 exit(1);
>         }
> 
>         addr = mmap(NULL, 4096, PROT_WRITE, MAP_SHARED|MAP_LOCKED, fd, 0);
>         if (addr == MAP_FAILED) {
>                 perror("mmap");
>                 exit(1);
>         }
>         munmap(addr, 4096);
>         close(fd);
> 
>         unlink(filename);
> }
> ==
> you'll see panic.
> 
> Fix is here
> ==
Hi Kame,

Thanks, The patch fixes the kernel panic.

Tested-by: Kamalesh Babulal <kamalesh@xxxxxxxxxxxxxxxxxx>
> 
> quick fix for double unlock_page();
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamewzawa.hiroyu@xxxxxxxxxxxxxx>
> Index: linux-2.6.26-rc5-mm3/mm/truncate.c
> ===================================================================
> --- linux-2.6.26-rc5-mm3.orig/mm/truncate.c
> +++ linux-2.6.26-rc5-mm3/mm/truncate.c
> @@ -104,8 +104,8 @@ truncate_complete_page(struct address_sp
> 
>  	cancel_dirty_page(page, PAGE_CACHE_SIZE);
> 
> -	remove_from_page_cache(page);
>  	clear_page_mlock(page);
> +	remove_from_page_cache(page);
>  	ClearPageUptodate(page);
>  	ClearPageMappedToDisk(page);
>  	page_cache_release(page);	/* pagecache ref */
> 


-- 
Thanks & Regards,
Kamalesh Babulal,
Linux Technology Center,
IBM, ISTL.
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