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authorJonathan Corbet <corbet@lwn.net>2008-12-05 16:12:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-12-05 15:35:10 -0800
commit218d11a8b071b23b76c484fd5f72a4fe3306801e (patch)
tree6656f841973496b0717117f8031d22bea019fd00 /fs
parentf2f1fa78a155524b849edf359e42a3001ea652c0 (diff)
downloadconfigs-218d11a8b071b23b76c484fd5f72a4fe3306801e.tar.gz
Fix a race condition in FASYNC handling
Changeset a238b790d5f99c7832f9b73ac8847025815b85f7 (Call fasync() functions without the BKL) introduced a race which could leave file->f_flags in a state inconsistent with what the underlying driver/filesystem believes. Revert that change, and also fix the same races in ioctl_fioasync() and ioctl_fionbio(). This is a minimal, short-term fix; the real fix will not involve the BKL. Reported-by: Oleg Nesterov <oleg@redhat.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: stable@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/fcntl.c7
-rw-r--r--fs/ioctl.c12
2 files changed, 15 insertions, 4 deletions
diff --git a/fs/fcntl.c b/fs/fcntl.c
index ac4f7db9f13..549daf8005f 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -19,6 +19,7 @@
#include <linux/signal.h>
#include <linux/rcupdate.h>
#include <linux/pid_namespace.h>
+#include <linux/smp_lock.h>
#include <asm/poll.h>
#include <asm/siginfo.h>
@@ -175,6 +176,11 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
if (error)
return error;
+ /*
+ * We still need a lock here for now to keep multiple FASYNC calls
+ * from racing with each other.
+ */
+ lock_kernel();
if ((arg ^ filp->f_flags) & FASYNC) {
if (filp->f_op && filp->f_op->fasync) {
error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
@@ -185,6 +191,7 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
out:
+ unlock_kernel();
return error;
}
diff --git a/fs/ioctl.c b/fs/ioctl.c
index d152856c371..43e8b2c0664 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -400,11 +400,9 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp,
/* Did FASYNC state change ? */
if ((flag ^ filp->f_flags) & FASYNC) {
- if (filp->f_op && filp->f_op->fasync) {
- lock_kernel();
+ if (filp->f_op && filp->f_op->fasync)
error = filp->f_op->fasync(fd, filp, on);
- unlock_kernel();
- } else
+ else
error = -ENOTTY;
}
if (error)
@@ -440,11 +438,17 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
break;
case FIONBIO:
+ /* BKL needed to avoid races tweaking f_flags */
+ lock_kernel();
error = ioctl_fionbio(filp, argp);
+ unlock_kernel();
break;
case FIOASYNC:
+ /* BKL needed to avoid races tweaking f_flags */
+ lock_kernel();
error = ioctl_fioasync(fd, filp, argp);
+ unlock_kernel();
break;
case FIOQSIZE: