Author: royger
Date: Wed May 20 11:01:10 2020
New Revision: 361274
URL: https://svnweb.freebsd.org/changeset/base/361274
Log:
dev/xenstore: fix return with locks held
Fix returning from xenstore device with locks held, which triggers the
following panic:
# cat /dev/xen/xenstore
^C
userret: returning with the following locks held:
exclusive sx evtchn_ringc_sx (evtchn_ringc_sx) r = 0 (0xfffff8000650be40)
locked @ /usr/src/sys/dev/xen/evtchn/evtchn_dev.c:262
Note this is not a security issue since access to the device is
limited to root by default.
Sponsored by: Citrix Systems R&D
MFC after: 1 week
Modified:
head/sys/dev/xen/evtchn/evtchn_dev.c
Modified: head/sys/dev/xen/evtchn/evtchn_dev.c
==============================================================================
--- head/sys/dev/xen/evtchn/evtchn_dev.c Wed May 20 08:15:09 2020
(r361273)
+++ head/sys/dev/xen/evtchn/evtchn_dev.c Wed May 20 11:01:10 2020
(r361274)
@@ -261,9 +261,10 @@ evtchn_read(struct cdev *dev, struct uio *uio, int iof
sx_xlock(&u->ring_cons_mutex);
for (;;) {
- error = EFBIG;
- if (u->ring_overflow)
+ if (u->ring_overflow) {
+ error = EFBIG;
goto unlock_out;
+ }
c = u->ring_cons;
p = u->ring_prod;
@@ -271,13 +272,13 @@ evtchn_read(struct cdev *dev, struct uio *uio, int iof
break;
if (ioflag & IO_NDELAY) {
- sx_xunlock(&u->ring_cons_mutex);
- return (EWOULDBLOCK);
+ error = EWOULDBLOCK;
+ goto unlock_out;
}
error = sx_sleep(u, &u->ring_cons_mutex, PCATCH, "evtchw", 0);
if ((error != 0) && (error != EWOULDBLOCK))
- return (error);
+ goto unlock_out;
}
/* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
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