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Fix a race condition in FASYNC handling

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Changeset a238b790d5 (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>
This commit is contained in:
Jonathan Corbet
2008-12-05 16:12:48 -07:00
committed by Linus Torvalds
parent f2f1fa78a1
commit 218d11a8b0
2 changed files with 15 additions and 4 deletions
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12
fs/ioctl.c
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@@ -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: