svn commit: r251756 - stable/9/sys/net
Guy Helmer
ghelmer at FreeBSD.org
Fri Jun 14 18:56:39 UTC 2013
Author: ghelmer
Date: Fri Jun 14 18:56:37 2013
New Revision: 251756
URL: http://svnweb.freebsd.org/changeset/base/251756
Log:
MFC r244090, r250945
Changes to resolve races in bpfread() and catchpacket() that, at worst,
cause kernel panics.
Add a flag to the bpf descriptor to indicate whether the hold buffer
is in use. In bpfread(), set the "hold buffer in use" flag before
dropping the descriptor lock during the call to bpf_uiomove().
Everywhere else the hold buffer is used or changed, wait while
the hold buffer is in use by bpfread(). Add a KASSERT in bpfread()
after re-acquiring the descriptor lock to assist uncovering any
additional hold buffer races.
While waiting for the bpf hold buffer to become idle, check
the return value from mtx_sleep() and exit bpfread() on
errors such as EINTR.
Modified:
stable/9/sys/net/bpf.c
stable/9/sys/net/bpf.h
stable/9/sys/net/bpf_buffer.c
stable/9/sys/net/bpfdesc.h
Directory Properties:
stable/9/sys/ (props changed)
stable/9/sys/net/ (props changed)
Modified: stable/9/sys/net/bpf.c
==============================================================================
--- stable/9/sys/net/bpf.c Fri Jun 14 18:42:08 2013 (r251755)
+++ stable/9/sys/net/bpf.c Fri Jun 14 18:56:37 2013 (r251756)
@@ -819,6 +819,7 @@ bpfopen(struct cdev *dev, int flags, int
* particular buffer method.
*/
bpf_buffer_init(d);
+ d->bd_hbuf_in_use = 0;
d->bd_bufmode = BPF_BUFMODE_BUFFER;
d->bd_sig = SIGIO;
d->bd_direction = BPF_D_INOUT;
@@ -872,6 +873,14 @@ bpfread(struct cdev *dev, struct uio *ui
callout_stop(&d->bd_callout);
timed_out = (d->bd_state == BPF_TIMED_OUT);
d->bd_state = BPF_IDLE;
+ while (d->bd_hbuf_in_use) {
+ error = mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock,
+ PRINET|PCATCH, "bd_hbuf", 0);
+ if (error != 0) {
+ BPFD_UNLOCK(d);
+ return (error);
+ }
+ }
/*
* If the hold buffer is empty, then do a timed sleep, which
* ends when the timeout expires or when enough packets
@@ -940,24 +949,27 @@ bpfread(struct cdev *dev, struct uio *ui
/*
* At this point, we know we have something in the hold slot.
*/
+ d->bd_hbuf_in_use = 1;
BPFD_UNLOCK(d);
/*
* Move data from hold buffer into user space.
* We know the entire buffer is transferred since
* we checked above that the read buffer is bpf_bufsize bytes.
- *
- * XXXRW: More synchronization needed here: what if a second thread
- * issues a read on the same fd at the same time? Don't want this
- * getting invalidated.
+ *
+ * We do not have to worry about simultaneous reads because
+ * we waited for sole access to the hold buffer above.
*/
error = bpf_uiomove(d, d->bd_hbuf, d->bd_hlen, uio);
BPFD_LOCK(d);
+ KASSERT(d->bd_hbuf != NULL, ("bpfread: lost bd_hbuf"));
d->bd_fbuf = d->bd_hbuf;
d->bd_hbuf = NULL;
d->bd_hlen = 0;
bpf_buf_reclaimed(d);
+ d->bd_hbuf_in_use = 0;
+ wakeup(&d->bd_hbuf_in_use);
BPFD_UNLOCK(d);
return (error);
@@ -1111,6 +1123,9 @@ reset_d(struct bpf_d *d)
BPFD_LOCK_ASSERT(d);
+ while (d->bd_hbuf_in_use)
+ mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock, PRINET,
+ "bd_hbuf", 0);
if ((d->bd_hbuf != NULL) &&
(d->bd_bufmode != BPF_BUFMODE_ZBUF || bpf_canfreebuf(d))) {
/* Free the hold buffer. */
@@ -1251,6 +1266,9 @@ bpfioctl(struct cdev *dev, u_long cmd, c
BPFD_LOCK(d);
n = d->bd_slen;
+ while (d->bd_hbuf_in_use)
+ mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock,
+ PRINET, "bd_hbuf", 0);
if (d->bd_hbuf)
n += d->bd_hlen;
BPFD_UNLOCK(d);
@@ -1964,6 +1982,9 @@ filt_bpfread(struct knote *kn, long hint
ready = bpf_ready(d);
if (ready) {
kn->kn_data = d->bd_slen;
+ while (d->bd_hbuf_in_use)
+ mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock,
+ PRINET, "bd_hbuf", 0);
if (d->bd_hbuf)
kn->kn_data += d->bd_hlen;
} else if (d->bd_rtout > 0 && d->bd_state == BPF_IDLE) {
@@ -2296,6 +2317,9 @@ catchpacket(struct bpf_d *d, u_char *pkt
* spot to do it.
*/
if (d->bd_fbuf == NULL && bpf_canfreebuf(d)) {
+ while (d->bd_hbuf_in_use)
+ mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock,
+ PRINET, "bd_hbuf", 0);
d->bd_fbuf = d->bd_hbuf;
d->bd_hbuf = NULL;
d->bd_hlen = 0;
@@ -2338,6 +2362,9 @@ catchpacket(struct bpf_d *d, u_char *pkt
++d->bd_dcount;
return;
}
+ while (d->bd_hbuf_in_use)
+ mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock,
+ PRINET, "bd_hbuf", 0);
ROTATE_BUFFERS(d);
do_wakeup = 1;
curlen = 0;
Modified: stable/9/sys/net/bpf.h
==============================================================================
--- stable/9/sys/net/bpf.h Fri Jun 14 18:42:08 2013 (r251755)
+++ stable/9/sys/net/bpf.h Fri Jun 14 18:56:37 2013 (r251756)
@@ -1235,7 +1235,8 @@ SYSCTL_DECL(_net_bpf);
/*
* Rotate the packet buffers in descriptor d. Move the store buffer into the
* hold slot, and the free buffer ino the store slot. Zero the length of the
- * new store buffer. Descriptor lock should be held.
+ * new store buffer. Descriptor lock should be held. Hold buffer must
+ * not be marked "in use".
*/
#define ROTATE_BUFFERS(d) do { \
(d)->bd_hbuf = (d)->bd_sbuf; \
Modified: stable/9/sys/net/bpf_buffer.c
==============================================================================
--- stable/9/sys/net/bpf_buffer.c Fri Jun 14 18:42:08 2013 (r251755)
+++ stable/9/sys/net/bpf_buffer.c Fri Jun 14 18:56:37 2013 (r251756)
@@ -79,6 +79,8 @@ __FBSDID("$FreeBSD$");
#include <net/bpf_buffer.h>
#include <net/bpfdesc.h>
+#define PRINET 26 /* interruptible */
+
/*
* Implement historical kernel memory buffering model for BPF: two malloc(9)
* kernel buffers are hung off of the descriptor. The size is fixed prior to
@@ -189,6 +191,9 @@ bpf_buffer_ioctl_sblen(struct bpf_d *d,
return (EINVAL);
}
+ while (d->bd_hbuf_in_use)
+ mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock,
+ PRINET, "bd_hbuf", 0);
/* Free old buffers if set */
if (d->bd_fbuf != NULL)
free(d->bd_fbuf, M_BPF);
Modified: stable/9/sys/net/bpfdesc.h
==============================================================================
--- stable/9/sys/net/bpfdesc.h Fri Jun 14 18:42:08 2013 (r251755)
+++ stable/9/sys/net/bpfdesc.h Fri Jun 14 18:56:37 2013 (r251756)
@@ -63,6 +63,7 @@ struct bpf_d {
caddr_t bd_sbuf; /* store slot */
caddr_t bd_hbuf; /* hold slot */
caddr_t bd_fbuf; /* free slot */
+ int bd_hbuf_in_use; /* don't rotate buffers */
int bd_slen; /* current length of store buffer */
int bd_hlen; /* current length of hold buffer */
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