Hello,
if you compile and run the below test case in an msdos or vfat directory
on an x86-64 system with -m32 you'll get garbage in the kernel_dirent
struct followed by a SIGSEGV.
The patch below fixes this. It's a minimal patch -- I haven't converted
spaces to tabs or added extra put_user checks.
The problems:
* d_ino/d_off are undefined for de[0]. Random values from the kernel stack
are copied here into user space.
* d_name, for both de[0] and de[1], is not zero terminated.
* if the long filename in de[1] is empty, d_ino/d_off are also undefined
for de[1].
Signed-off-by: Bart Oldeman <[email protected]>
testcase:
#include <sys/types.h>
#include <sys/ioctl.h>
#include <dirent.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
struct kernel_dirent {
long d_ino;
long d_off;
unsigned short d_reclen;
char d_name[256]; /* We must not include limits.h! */
};
#define VFAT_IOCTL_READDIR_BOTH _IOR('r', 1, struct kernel_dirent [2])
#define VFAT_IOCTL_READDIR_SHORT _IOR('r', 2, struct kernel_dirent [2])
int main(void)
{
int fd = open(".", O_RDONLY);
struct kernel_dirent de[2];
while (1) {
int i = ioctl(fd, VFAT_IOCTL_READDIR_BOTH, (long)de);
if (i == -1) break;
if (de[0].d_reclen == 0) break;
printf("SFN: reclen=%2d off=%d ino=%d, %-12s",
de[0].d_reclen, de[0].d_off, de[0].d_ino, de[0].d_name);
if (de[1].d_reclen)
printf("\tLFN: reclen=%2d off=%d ino=%d, %s",
de[1].d_reclen, de[1].d_off, de[1].d_ino, de[1].d_name);
printf("\n");
}
return 0;
}
Patch:
--- linux-2.6/fs/fat/dir.c.orig 2007-04-29 12:41:04.000000000 -0400
+++ linux-2.6/fs/fat/dir.c 2007-04-29 13:59:45.000000000 -0400
@@ -749,14 +749,23 @@ static int fat_dir_ioctl(struct inode *
static long fat_compat_put_dirent32(struct dirent *d,
struct compat_dirent __user *d32)
{
- if (!access_ok(VERIFY_WRITE, d32, sizeof(struct compat_dirent)))
+ if (!access_ok(VERIFY_WRITE, d32, sizeof(struct compat_dirent[2])))
return -EFAULT;
- __put_user(d->d_ino, &d32->d_ino);
- __put_user(d->d_off, &d32->d_off);
__put_user(d->d_reclen, &d32->d_reclen);
+ __put_user(0, d32->d_name + d->d_reclen);
if (__copy_to_user(d32->d_name, d->d_name, d->d_reclen))
return -EFAULT;
+ d++;
+ d32++;
+ __put_user(d->d_reclen, &d32->d_reclen);
+ __put_user(0, d32->d_name + d->d_reclen);
+ if (d->d_reclen) {
+ __put_user(d->d_ino, &d32->d_ino);
+ __put_user(d->d_off, &d32->d_off);
+ if (__copy_to_user(d32->d_name, d->d_name, d->d_reclen))
+ return -EFAULT;
+ }
return 0;
}
@@ -787,8 +796,7 @@ static long fat_compat_dir_ioctl(struct
unlock_kernel();
set_fs(oldfs);
if (ret >= 0) {
- ret |= fat_compat_put_dirent32(&d[0], p);
- ret |= fat_compat_put_dirent32(&d[1], p + 1);
+ ret |= fat_compat_put_dirent32(d, p);
}
return ret;
}
-
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