[PATCH] files: fix preemption issues
With the new fdtable locking rules, you have to protect fdtable with either
->file_lock or rcu_read_lock/unlock(). There are some places where we
aren't doing either. This patch fixes those places.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index 0636116..01fe990 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c
@@ -37,6 +37,7 @@
#include <linux/namei.h>
#include <linux/uio.h>
#include <linux/vfs.h>
+#include <linux/rcupdate.h>
#include <asm/fpu.h>
#include <asm/io.h>
@@ -975,6 +976,7 @@
long timeout;
int ret = -EINVAL;
struct fdtable *fdt;
+ int max_fdset;
timeout = MAX_SCHEDULE_TIMEOUT;
if (tvp) {
@@ -996,8 +998,11 @@
}
}
+ rcu_read_lock();
fdt = files_fdtable(current->files);
- if (n < 0 || n > fdt->max_fdset)
+ max_fdset = fdt->max_fdset;
+ rcu_read_unlock();
+ if (n < 0 || n > max_fdset)
goto out_nofds;
/*
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index af42cda..d71731e 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -2218,12 +2218,13 @@
pfm_free_fd(int fd, struct file *file)
{
struct files_struct *files = current->files;
- struct fdtable *fdt = files_fdtable(files);
+ struct fdtable *fdt;
/*
* there ie no fd_uninstall(), so we do it here
*/
spin_lock(&files->file_lock);
+ fdt = files_fdtable(files);
rcu_assign_pointer(fdt->fd[fd], NULL);
spin_unlock(&files->file_lock);
diff --git a/fs/locks.c b/fs/locks.c
index c2c09b4..f7daa5f 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -124,6 +124,7 @@
#include <linux/smp_lock.h>
#include <linux/syscalls.h>
#include <linux/time.h>
+#include <linux/rcupdate.h>
#include <asm/semaphore.h>
#include <asm/uaccess.h>
@@ -2205,6 +2206,7 @@
lock_kernel();
j = 0;
+ rcu_read_lock();
fdt = files_fdtable(files);
for (;;) {
unsigned long set;
@@ -2222,6 +2224,7 @@
set >>= 1;
}
}
+ rcu_read_unlock();
unlock_kernel();
}
EXPORT_SYMBOL(steal_locks);
diff --git a/fs/proc/array.c b/fs/proc/array.c
index d88d518..d84eeca 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -74,6 +74,7 @@
#include <linux/file.h>
#include <linux/times.h>
#include <linux/cpuset.h>
+#include <linux/rcupdate.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -180,12 +181,14 @@
p->gid, p->egid, p->sgid, p->fsgid);
read_unlock(&tasklist_lock);
task_lock(p);
+ rcu_read_lock();
if (p->files)
fdt = files_fdtable(p->files);
buffer += sprintf(buffer,
"FDSize:\t%d\n"
"Groups:\t",
fdt ? fdt->max_fds : 0);
+ rcu_read_unlock();
group_info = p->group_info;
get_group_info(group_info);
diff --git a/kernel/exit.c b/kernel/exit.c
index 6d2089a..ee6d8b8 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -371,6 +371,12 @@
struct fdtable *fdt;
j = 0;
+
+ /*
+ * It is safe to dereference the fd table without RCU or
+ * ->file_lock because this is the last reference to the
+ * files structure.
+ */
fdt = files_fdtable(files);
for (;;) {
unsigned long set;