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/proc/self/maps doesn't display the real file offset 

This addresses

	http://bugzilla.kernel.org/show_bug.cgi?id=11318

In function show_map (file: fs/proc/task_mmu.c), if vma->vm_pgoff > 2^20
than (vma->vm_pgoff << PAGE_SIZE) is greater than 2^32 (with PAGE_SIZE
equal to 4096 (i.e.  2^12).  The next seq_printf use an unsigned long for
the conversion of (vma->vm_pgoff << PAGE_SIZE), as a result the offset
value displayed in /proc/self/maps is truncated if the page offset is
greater than 2^20.

A test that shows this issue:

#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

#define PAGE_SIZE (getpagesize())

#if __i386__
#   define U64_STR "%llx"
#elif __x86_64
#   define U64_STR "%lx"
#else
#   error "Architecture Unsupported"
#endif

int main(int argc, char *argv[])
{
	int fd;
	char *addr;
	off64_t offset = 0x10000000;
	char *filename = "/dev/zero";

	fd = open(filename, O_RDONLY);
	if (fd < 0) {
		perror("open");
		return 1;
	}

	offset *= 0x10;
	printf("offset = " U64_STR "\n", offset);

	addr = (char*)mmap64(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE, fd,
			     offset);
	if ((void*)addr == MAP_FAILED) {
		perror("mmap64");
		return 1;
	}

	{
		FILE *fmaps;
		char *line = NULL;
		size_t len = 0;
		ssize_t read;
		size_t filename_len = strlen(filename);

		fmaps = fopen("/proc/self/maps", "r");
		if (!fmaps) {
			perror("fopen");
			return 1;
		}
		while ((read = getline(&line, &len, fmaps)) != -1) {
			if ((read > filename_len + 1)
			    && (strncmp(&line[read - filename_len - 1], filename, filename_len) == 0))
				printf("%s", line);
		}

		if (line)
			free(line);

		fclose(fmaps);
	}

	close(fd);
	return 0;
}

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Clement Calmels <cboulte@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Clement Calmels 2008-08-20 14:09:00 -07:00 committed by Linus Torvalds
parent 35fc908dc0
commit 1804dc6e14
2 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/proc/nommu.c
View File

@ -52,14 +52,14 @@ int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma)
}
seq_printf(m,
"%08lx-%08lx %c%c%c%c %08lx %02x:%02x %lu %n",
"%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
vma->vm_start,
vma->vm_end,
flags & VM_READ ? 'r' : '-',
flags & VM_WRITE ? 'w' : '-',
flags & VM_EXEC ? 'x' : '-',
flags & VM_MAYSHARE ? flags & VM_SHARED ? 'S' : 's' : 'p',
vma->vm_pgoff << PAGE_SHIFT,
((loff_t)vma->vm_pgoff) << PAGE_SHIFT,
MAJOR(dev), MINOR(dev), ino, &len);
if (file) {

4
fs/proc/task_mmu.c
View File

@ -219,14 +219,14 @@ static int show_map(struct seq_file *m, void *v)
ino = inode->i_ino;
}
seq_printf(m, "%08lx-%08lx %c%c%c%c %08lx %02x:%02x %lu %n",
seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
vma->vm_start,
vma->vm_end,
flags & VM_READ ? 'r' : '-',
flags & VM_WRITE ? 'w' : '-',
flags & VM_EXEC ? 'x' : '-',
flags & VM_MAYSHARE ? 's' : 'p',
vma->vm_pgoff << PAGE_SHIFT,
((loff_t)vma->vm_pgoff) << PAGE_SHIFT,
MAJOR(dev), MINOR(dev), ino, &len);
/*