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From: Jilles Tjoelker <jilles@FreeBSD.org>
Date: Thu, 23 Jun 2016 20:59:13 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r302151 - head/sys/kern
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Author: jilles
Date: Thu Jun 23 20:59:13 2016
New Revision: 302151
URL: https://svnweb.freebsd.org/changeset/base/302151

Log:
  posixshm: Fix lock leak when mac_posixshm_check_read rejects read.
  
  While reading the code, I noticed that shm_read() returns without unlocking
  foffset and rangelock if mac_posixshm_check_read() rejects the read.
  
  Reviewed by:	kib, jhb, rwatson
  Approved by:	re (gjb)
  MFC after:	1 week
  Differential Revision:	https://reviews.freebsd.org/D6927

Modified:
  head/sys/kern/uipc_shm.c

Modified: head/sys/kern/uipc_shm.c
==============================================================================
--- head/sys/kern/uipc_shm.c	Thu Jun 23 20:05:59 2016	(r302150)
+++ head/sys/kern/uipc_shm.c	Thu Jun 23 20:59:13 2016	(r302151)
@@ -295,14 +295,14 @@ shm_read(struct file *fp, struct uio *ui
 	int error;
 
 	shmfd = fp->f_data;
-	foffset_lock_uio(fp, uio, flags);
-	rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
-	    uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
 #ifdef MAC
 	error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
 	if (error)
 		return (error);
 #endif
+	foffset_lock_uio(fp, uio, flags);
+	rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
+	    uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
 	error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
 	rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 	foffset_unlock_uio(fp, uio, flags);