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Fix a race condition in FASYNC handling
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:
parent
f2f1fa78a1
commit
218d11a8b0
@ -19,6 +19,7 @@
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#include <linux/signal.h>
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#include <linux/rcupdate.h>
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#include <linux/pid_namespace.h>
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#include <linux/smp_lock.h>
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#include <asm/poll.h>
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#include <asm/siginfo.h>
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@ -175,6 +176,11 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
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if (error)
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return error;
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/*
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* We still need a lock here for now to keep multiple FASYNC calls
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* from racing with each other.
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*/
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lock_kernel();
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if ((arg ^ filp->f_flags) & FASYNC) {
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if (filp->f_op && filp->f_op->fasync) {
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error = filp->f_op->fasync(fd, filp, (arg & FASYNC) != 0);
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@ -185,6 +191,7 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
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filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
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out:
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unlock_kernel();
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return error;
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}
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12
fs/ioctl.c
12
fs/ioctl.c
@ -400,11 +400,9 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp,
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/* Did FASYNC state change ? */
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if ((flag ^ filp->f_flags) & FASYNC) {
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if (filp->f_op && filp->f_op->fasync) {
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lock_kernel();
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if (filp->f_op && filp->f_op->fasync)
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error = filp->f_op->fasync(fd, filp, on);
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unlock_kernel();
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} else
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else
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error = -ENOTTY;
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}
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if (error)
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@ -440,11 +438,17 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
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break;
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case FIONBIO:
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/* BKL needed to avoid races tweaking f_flags */
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lock_kernel();
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error = ioctl_fionbio(filp, argp);
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unlock_kernel();
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break;
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case FIOASYNC:
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/* BKL needed to avoid races tweaking f_flags */
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lock_kernel();
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error = ioctl_fioasync(fd, filp, argp);
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unlock_kernel();
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break;
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case FIOQSIZE:
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