diff options
| author | Jonathan Corbet <corbet@lwn.net> | 2008-12-05 16:12:48 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-12-05 15:35:10 -0800 |
| commit | 218d11a8b071b23b76c484fd5f72a4fe3306801e (patch) | |
| tree | 6656f841973496b0717117f8031d22bea019fd00 | |
| parent | f2f1fa78a155524b849edf359e42a3001ea652c0 (diff) | |
| download | op-kernel-dev-218d11a8b071b23b76c484fd5f72a4fe3306801e.zip op-kernel-dev-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>
| -rw-r--r-- | fs/fcntl.c | 7 | ||||
| -rw-r--r-- | fs/ioctl.c | 12 |
2 files changed, 15 insertions, 4 deletions
@@ -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; } @@ -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: |
