[PATCH 3.2 74/77] af_unix: Revert 'lock_interruptible' in stream receive code

From	Ben Hutchings <ben@decadent.org.uk>
Newsgroups	linux.kernel
Subject	[PATCH 3.2 74/77] af_unix: Revert 'lock_interruptible' in stream receive code
Date	2015-12-24 17:10 +0100
Message-ID	<qJgCL-u9-21@gated-at.bofh.it> (permalink)
References	<qJgjn-6R-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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3.2.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Rainer Weikusat <rweikusat@mobileactivedefense.com>

[ Upstream commit 3822b5c2fc62e3de8a0f33806ff279fb7df92432 ]

With b3ca9b02b00704053a38bfe4c31dbbb9c13595d0, the AF_UNIX SOCK_STREAM
receive code was changed from using mutex_lock(&u->readlock) to
mutex_lock_interruptible(&u->readlock) to prevent signals from being
delayed for an indefinite time if a thread sleeping on the mutex
happened to be selected for handling the signal. But this was never a
problem with the stream receive code (as opposed to its datagram
counterpart) as that never went to sleep waiting for new messages with the
mutex held and thus, wouldn't cause secondary readers to block on the
mutex waiting for the sleeping primary reader. As the interruptible
locking makes the code more complicated in exchange for no benefit,
change it back to using mutex_lock.

Signed-off-by: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 net/unix/af_unix.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1913,14 +1913,7 @@ static int unix_dgram_recvmsg(struct kio
 	if (flags&MSG_OOB)
 		goto out;
 
-	err = mutex_lock_interruptible(&u->readlock);
-	if (unlikely(err)) {
-		/* recvmsg() in non blocking mode is supposed to return -EAGAIN
-		 * sk_rcvtimeo is not honored by mutex_lock_interruptible()
-		 */
-		err = noblock ? -EAGAIN : -ERESTARTSYS;
-		goto out;
-	}
+	mutex_lock(&u->readlock);
 
 	skb = skb_recv_datagram(sk, flags, noblock, &err);
 	if (!skb) {
@@ -2105,12 +2098,12 @@ static int unix_stream_recvmsg(struct ki
 
 			timeo = unix_stream_data_wait(sk, timeo);
 
-			if (signal_pending(current)
-			    ||  mutex_lock_interruptible(&u->readlock)) {
+			if (signal_pending(current)) {
 				err = sock_intr_errno(timeo);
 				goto out;
 			}
 
+			mutex_lock(&u->readlock);
 			continue;
  unlock:
 			unix_state_unlock(sk);

--
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Thread

[PATCH 3.2 00/77] 3.2.75-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 16:50 +0100
  [PATCH 3.2 43/77] dm btree: fix leak of bufio-backed block in  btree_split_sibling error path Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 73/77] bluetooth: Validate socket address length in   sco_sock_bind(). Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 31/77] broadcom: fix PHY_ID_BCM5481 entry in the id table Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 08/77] USB: ti_usb_3410_502: Fix ID table size Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 04/77] ALSA: usb-audio: prevent CH345 multiport output  SysEx corruption Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 76/77] isdn_ppp: Add checks for allocation failure in  isdn_ppp_open() Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 18/77] USB: option: add XS Stick W100-2 from 4G Systems Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 28/77] fix sysvfs symlinks Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 56/77] mm, vmstat: allow WQ concurrency to discover  memory reclaim doesn't make any progress Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 22/77] net: ip6mr: fix static mfc/dev leaks on table  destruction Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 37/77] drm/ttm: Fixed a read/write lock imbalance Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 52/77] ipmi: move timer init to before irq is setup Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 50/77] ALSA: rme96: Fix unexpected volume reset after  rate changes Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 64/77] dccp: remove unnecessary codes in ipv6.c Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 68/77] sctp: update the netstamp_needed counter when  copying  sockets Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 16/77] xhci: Add XHCI_INTEL_HOST quirk Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 15/77] macvlan: fix leak in macvlan_handle_frame Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 65/77] ipv6: add complete rcu protection around np->opt Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 09/77] USB: ti_usb_3410_5052: Add Honeywell HGI80 ID Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 17/77] xhci: Workaround to get Intel xHCI reset  working more reliably Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 05/77] ALSA: usb-audio: work around CH345 input SysEx  corruption Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 67/77] atl1c: Improve driver not to do order 4  GFP_ATOMIC  allocation Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 19/77] usblp: do not set TASK_INTERRUPTIBLE before lock Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 55/77] parisc iommu: fix panic due to trying to  allocate too large region Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 62/77] net: ipmr: fix static mfc/dev leaks on table   destruction Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 30/77] vfs: Avoid softlockups with sendfile(2) Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 10/77] usb: musb: core: fix order of arguments to ulpi  write callback Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 59/77] snmp: Remove duplicate OUTMCAST stat increment Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 24/77] USB: cp210x: Remove CP2110 ID from  compatibility list Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 46/77] drm: Fix an unwanted master inheritance v2 Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
    Re: [PATCH 3.2 46/77] drm: Fix an unwanted master inheritance v2 Thomas Hellstrom <thellstrom@vmware.com> - 2015-12-25 15:20 +0100
      Re: [PATCH 3.2 46/77] drm: Fix an unwanted master inheritance v2 Ben Hutchings <ben@decadent.org.uk> - 2015-12-26 05:40 +0100
  [PATCH 3.2 66/77] ipv6: sctp: implement sctp_v6_destroy_sock() Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 06/77] USB: serial: option: add support for Novatel  MiFi USB620L Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 71/77] sh_eth: fix kernel oops in skb_put() Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 14/77] mac80211: mesh: fix call_rcu() usage Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:00 +0100
  [PATCH 3.2 49/77] usb: xhci: fix config fail of FS hub behind a  HS hub with MTT Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 54/77] vgaarb: fix signal handling in vga_get() Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 58/77] sh64: fix __NR_fgetxattr Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 70/77] net: add validation for the socket syscall  protocol  argument Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 40/77] wan/x25: Fix use-after-free in x25_asy_open_tty() Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 44/77] ipv4: igmp: Allow removing groups from a  removed interface Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 03/77] ALSA: usb-audio: add packet size quirk for the  Medeli DD305 Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 53/77] dm btree: fix bufio buffer leaks in  dm_btree_del() error path Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 74/77] af_unix: Revert 'lock_interruptible' in stream  receive  code Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 47/77] sched/core: Remove false-positive warning from  wake_up_process() Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 75/77] af_unix: fix a fatal race with bit fields Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 45/77] locking: Add WARN_ON_ONCE lock assertion Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 35/77] RDS: fix race condition when sending a message  on unbound socket Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 77/77] ppp, slip: Validate VJ compression slot  parameters completely Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 41/77] USB: whci-hcd: add check for dma mapping error Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 51/77] 9p: ->evict_inode() should kick out ->i_data,  not ->i_mapping Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 38/77] AHCI: Fix softreset failed issue of Port Multiplier Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 39/77] sata_sil: disable trim Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  [PATCH 3.2 36/77] nfs: if we have no valid attrs, then don't  declare the attribute cache valid Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 17:10 +0100
  Re: [PATCH 3.2 00/77] 3.2.75-rc1 review Guenter Roeck <linux@roeck-us.net> - 2015-12-24 23:30 +0100
    Re: [PATCH 3.2 00/77] 3.2.75-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2015-12-24 23:40 +0100

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