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Subjectremap_file_pages() broken in 2.6.23?
Original report: https://bugzilla.redhat.com/show_bug.cgi?id=404201

The test case below, taken from the LTP test code, prints -1 (as
expected) on 2.6.22 and 0 on 2.6.23. It tries to remap an out-of-range
page. Proposed patch follows the program. Bug was apparently caused by
commit 54cb8821de07f2ffcd28c380ce9b93d5784b40d7.

/*
* originally remap_file_pages02.c, from LTP
* - creates the file 'cache'; no cleanup
*
* Copyright (C) Ricardo Salveti de Araujo, 2007
*
* GPL v2
*/
#define _GNU_SOURCE
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <syscall.h>
#include <stdlib.h>
#include <linux/unistd.h>

/* Test case defines */
#define WINDOW_START 0x48000000
size_t page_sz;
size_t page_words;
size_t cache_pages;
size_t cache_sz;
size_t window_pages;
size_t window_sz;

static char *cache_contents;
int fd; /* File descriptor used at the test */
char *data = NULL;
char *data01 = NULL;
int
main(int ac, char **av)
{
int i, j, ret;
page_sz = getpagesize();
page_words = (page_sz/sizeof(char));

/* Set the cache size */
cache_pages = 32;
cache_sz = cache_pages*page_sz;
cache_contents = (char *) malloc(cache_sz * sizeof(char));
for (i = 0; i < cache_pages; i++) {
char *page = cache_contents + i*page_sz;
for (j = 0; j < page_words; j++)
page[j] = i;
}
if ((fd = open("cache", O_RDWR|O_CREAT|O_TRUNC,S_IRWXU)) < 0)
perror("open"), exit(1);
if (write(fd, cache_contents, cache_sz) != cache_sz)
perror("write"), exit(1);
data = mmap((void *)WINDOW_START,
cache_sz,
PROT_READ|PROT_WRITE,
MAP_FIXED | MAP_SHARED,
fd, 0);
if (data == MAP_FAILED)
perror("mmap"), exit(1);
ret = remap_file_pages(data, page_sz, 0, cache_pages * 2, 0);

printf("%d\n", ret);

exit(0);
}
Patch:

Signed-off-by: Supriya Kannery <supriyak@in.ibm.com>

--- linux-2.6.23/mm/fremap.c.orig 2007-11-22 00:56:09.000000000 -0600
+++ linux-2.6.23/mm/fremap.c 2007-11-26 03:08:55.000000000 -0600
@@ -124,6 +124,7 @@ asmlinkage long sys_remap_file_pages(uns
struct vm_area_struct *vma;
int err = -EINVAL;
int has_write_lock = 0;
+ unsigned long f_size = 0;

if (__prot)
return err;
@@ -181,6 +182,14 @@ asmlinkage long sys_remap_file_pages(uns
goto retry;
}
mapping = vma->vm_file->f_mapping;
+
+ f_size = i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1;
+ f_size = f_size >> PAGE_CACHE_SHIFT;
+ if ((pgoff + size >> PAGE_CACHE_SHIFT) > f_size) {
+ err = -EINVAL;
+ goto out;
+ }
+
/*
* page_mkclean doesn't work on nonlinear vmas, so if
* dirty pages need to be accounted, emulate with linear
-
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