Messages in this thread Patch in this message | | | Date | Thu, 11 Dec 2008 11:14:00 -0800 | From | Greg KH <> | Subject | [patch 14/83] Fix a race condition in FASYNC handling |
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2.6.27-stable review patch. If anyone has any objections, please let us know.
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From: Jonathan Corbet <corbet@lwn.net>
commit 218d11a8b071b23b76c484fd5f72a4fe3306801e upstream.
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> Signed-off-by: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- fs/fcntl.c | 7 +++++++ fs/ioctl.c | 12 ++++++++---- 2 files changed, 15 insertions(+), 4 deletions(-)
--- 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 * f 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 * f filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK); out: + unlock_kernel(); return error; } --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -123,11 +123,9 @@ static int ioctl_fioasync(unsigned int f /* 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) @@ -163,11 +161,17 @@ int do_vfs_ioctl(struct file *filp, unsi 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:
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