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Subject[PATCH] files_struct race conditions fixes
Hi Andrea,

Based on Maneesh's audit of the fields of files_struct, it seems
that there are a few places where the file pointers are
being looked up without holding the reader side of the
rwlock in files_struct. This can lead to a race with another cloned task
that may share the files_struct.

Here is a patch that fixes the affected places.

Thanks
Dipankar
--
Dipankar Sarma <dipankar@in.ibm.com> http://lse.sourceforge.net
Linux Technology Center, IBM Software Lab, Bangalore, India.

diff -urN linux-2.4.14/arch/ia64/ia32/sys_ia32.c linux-2.4.14+files/arch/ia64/ia32/sys_ia32.c
--- linux-2.4.14/arch/ia64/ia32/sys_ia32.c Mon Aug 13 03:37:42 2001
+++ linux-2.4.14+files/arch/ia64/ia32/sys_ia32.c Mon Nov 12 14:35:54 2001
@@ -3853,7 +3853,9 @@
}
/* Bump the usage count and install the file. */
fp[i]->f_count++;
+ write_lock(&current->files->file_lock);
current->files->fd[new_fd] = fp[i];
+ write_unlock(&current->files->file_lock);
}

if (i > 0) {
diff -urN linux-2.4.14/arch/sparc/kernel/sunos_ioctl.c linux-2.4.14+files/arch/sparc/kernel/sunos_ioctl.c
--- linux-2.4.14/arch/sparc/kernel/sunos_ioctl.c Thu Sep 7 21:02:00 2000
+++ linux-2.4.14+files/arch/sparc/kernel/sunos_ioctl.c Mon Nov 12 14:40:23 2001
@@ -39,8 +39,12 @@
{
int ret = -EBADF;

- if (fd >= SUNOS_NR_OPEN || !fcheck(fd))
+ read_lock(&current->files->file_lock);
+ if (fd >= SUNOS_NR_OPEN || !fcheck(fd)) {
+ read_unlock(&current->files->file_lock);
goto out;
+ }
+ read_unlock(&current->files->file_lock);

/* First handle an easy compat. case for tty ldisc. */
if(cmd == TIOCSETD) {
diff -urN linux-2.4.14/arch/sparc64/kernel/sunos_ioctl32.c linux-2.4.14+files/arch/sparc64/kernel/sunos_ioctl32.c
--- linux-2.4.14/arch/sparc64/kernel/sunos_ioctl32.c Sat Aug 5 06:46:11 2000
+++ linux-2.4.14+files/arch/sparc64/kernel/sunos_ioctl32.c Mon Nov 12 14:42:51 2001
@@ -100,8 +100,12 @@

if(fd >= SUNOS_NR_OPEN)
goto out;
- if(!fcheck(fd))
+ read_lock(&current->files->file_lock);
+ if(!fcheck(fd)) {
+ read_unlock(&current->files->file_lock);
goto out;
+ }
+ read_unlock(&current->files->file_lock);

if(cmd == TIOCSETD) {
mm_segment_t old_fs = get_fs();
diff -urN linux-2.4.14/arch/sparc64/solaris/ioctl.c linux-2.4.14+files/arch/sparc64/solaris/ioctl.c
--- linux-2.4.14/arch/sparc64/solaris/ioctl.c Wed Nov 29 11:23:44 2000
+++ linux-2.4.14+files/arch/sparc64/solaris/ioctl.c Mon Nov 12 14:33:48 2001
@@ -289,11 +289,15 @@
{
struct inode *ino;
/* I wonder which of these tests are superfluous... --patrik */
+ read_lock(&current->files->file_lock);
if (! current->files->fd[fd] ||
! current->files->fd[fd]->f_dentry ||
! (ino = current->files->fd[fd]->f_dentry->d_inode) ||
- ! ino->i_sock)
+ ! ino->i_sock) {
+ read_unlock(&current->files->file_lock);
return TBADF;
+ }
+ read_unlock(&current->files->file_lock);

switch (cmd & 0xff) {
case 109: /* SI_SOCKPARAMS */
diff -urN linux-2.4.14/arch/sparc64/solaris/timod.c linux-2.4.14+files/arch/sparc64/solaris/timod.c
--- linux-2.4.14/arch/sparc64/solaris/timod.c Fri Sep 21 02:41:57 2001
+++ linux-2.4.14+files/arch/sparc64/solaris/timod.c Mon Nov 12 14:31:19 2001
@@ -149,7 +149,9 @@
struct socket *sock;

SOLD("wakeing socket");
+ read_lock(&current->files->file_lock);
sock = &current->files->fd[fd]->f_dentry->d_inode->u.socket_i;
+ read_unlock(&current->files->file_lock);
wake_up_interruptible(&sock->wait);
read_lock(&sock->sk->callback_lock);
if (sock->fasync_list && !test_bit(SOCK_ASYNC_WAITDATA, &sock->flags))
@@ -163,7 +165,9 @@
struct sol_socket_struct *sock;

SOLD("queuing primsg");
+ read_lock(&current->files->file_lock);
sock = (struct sol_socket_struct *)current->files->fd[fd]->private_data;
+ read_unlock(&current->files->file_lock);
it->next = sock->pfirst;
sock->pfirst = it;
if (!sock->plast)
@@ -177,7 +181,9 @@
struct sol_socket_struct *sock;

SOLD("queuing primsg at end");
+ read_lock(&current->files->file_lock);
sock = (struct sol_socket_struct *)current->files->fd[fd]->private_data;
+ read_unlock(&current->files->file_lock);
it->next = NULL;
if (sock->plast)
sock->plast->next = it;
@@ -355,7 +361,11 @@
(int (*)(int, unsigned long *))SYS(socketcall);
int (*sys_sendto)(int, void *, size_t, unsigned, struct sockaddr *, int) =
(int (*)(int, void *, size_t, unsigned, struct sockaddr *, int))SYS(sendto);
- filp = current->files->fd[fd];
+ read_lock(&current->files->file_lock);
+ filp = fcheck(fd);
+ read_unlock(&current->files->file_lock);
+ if (!filp)
+ return -EBADF;
ino = filp->f_dentry->d_inode;
sock = (struct sol_socket_struct *)filp->private_data;
SOLD("entry");
@@ -636,7 +646,11 @@

SOLD("entry");
SOLDD(("%u %p %d %p %p %d %p %d\n", fd, ctl_buf, ctl_maxlen, ctl_len, data_buf, data_maxlen, data_len, *flags_p));
- filp = current->files->fd[fd];
+ read_lock(&current->files->file_lock);
+ filp = fcheck(fd);
+ read_unlock(&current->files->file_lock);
+ if (!filp)
+ return -EBADF;
ino = filp->f_dentry->d_inode;
sock = (struct sol_socket_struct *)filp->private_data;
SOLDD(("%p %p\n", sock->pfirst, sock->pfirst ? sock->pfirst->next : NULL));
@@ -847,7 +861,9 @@
lock_kernel();
if(fd >= NR_OPEN) goto out;

- filp = current->files->fd[fd];
+ read_lock(&current->files->file_lock);
+ filp = fcheck(fd);
+ read_unlock(&current->files->file_lock);
if(!filp) goto out;

ino = filp->f_dentry->d_inode;
@@ -914,7 +930,9 @@
lock_kernel();
if(fd >= NR_OPEN) goto out;

- filp = current->files->fd[fd];
+ read_lock(&current->files->file_lock);
+ filp = fcheck(fd);
+ read_unlock(&current->files->file_lock);
if(!filp) goto out;

ino = filp->f_dentry->d_inode;
diff -urN linux-2.4.14/fs/proc/base.c linux-2.4.14+files/fs/proc/base.c
--- linux-2.4.14/fs/proc/base.c Thu Oct 11 12:12:47 2001
+++ linux-2.4.14+files/fs/proc/base.c Mon Nov 12 12:53:58 2001
@@ -553,6 +553,7 @@
task_unlock(p);
if (!files)
goto out;
+ read_lock(&files->file_lock);
for (fd = filp->f_pos-2;
fd < files->max_fds;
fd++, filp->f_pos++) {
@@ -573,6 +574,7 @@
if (filldir(dirent, buf+j, NUMBUF-j, fd+2, ino, DT_LNK) < 0)
break;
}
+ read_unlock(&files->file_lock);
put_files_struct(files);
}
out:
-
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