]>
git.openfabrics.org - ~emulex/infiniband.git/commit
tty,vcs: lseek/VC-release race fix
there's a race between vcs's lseek handler and VC release.
The lseek handler does not hold console_lock and touches
VC's size info. If during this the VC got released, there's
an access violation.
Following program triggers the issue for me:
[SNIP]
#define _BSD_SOURCE
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/vt.h>
#include <unistd.h>
#include <errno.h>
static int run_seek(void)
{
while(1) {
int fd;
fd = open("./vcs30", O_RDWR);
while(lseek(fd, 0, 0) != -1);
close(fd);
}
}
static int open_ioctl_tty(void)
{
return open("/dev/tty1", O_RDWR);
}
static int do_ioctl(int fd, int req, int i)
{
return ioctl(fd, req, i);
}
#define INIT(i) do_ioctl(ioctl_fd, VT_ACTIVATE, i)
#define SHUT(i) do_ioctl(ioctl_fd, VT_DISALLOCATE, i)
int main(int argc, char **argv)
{
int ioctl_fd = open_ioctl_tty();
if (ioctl < 0) {
perror("open tty1 failed\n");
return -1;
}
if ((-1 == mknod("vcs30", S_IFCHR|0666, makedev(7, 30))) &&
(errno != EEXIST)) {
printf("errno %d\n", errno);
perror("failed to create vcs30");
return -1;
}
do_ioctl(ioctl_fd, VT_LOCKSWITCH, 0);
if (!fork())
run_seek();
while(1) {
INIT(30);
SHUT(30);
}
return 0;
}
[SNIP]
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>