From 218d11a8b071b23b76c484fd5f72a4fe3306801e Mon Sep 17 00:00:00 2001 From: Jonathan Corbet Date: Fri, 5 Dec 2008 16:12:48 -0700 Subject: [PATCH] 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 Cc: Andi Kleen Cc: Al Viro Cc: stable@kernel.org Signed-off-by: Jonathan Corbet Signed-off-by: Linus Torvalds --- fs/fcntl.c | 7 +++++++ fs/ioctl.c | 12 ++++++++---- 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 #include #include +#include #include #include @@ -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: -- 2.41.1