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Date:      Fri, 28 Oct 2016 11:35:07 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r308025 - head/sys/fs/msdosfs
Message-ID:  <201610281135.u9SBZ7Kk004640@repo.freebsd.org>
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Author: kib
Date: Fri Oct 28 11:35:06 2016
New Revision: 308025
URL: https://svnweb.freebsd.org/changeset/base/308025

Log:
  Enable vn_io_fault() deadlock avoidance for msdosfs.
  
  Reported and tested by:	pho
  Sponsored by:	The FreeBSD Foundation
  MFC after:	2 weeks

Modified:
  head/sys/fs/msdosfs/msdosfs_vfsops.c
  head/sys/fs/msdosfs/msdosfs_vnops.c

Modified: head/sys/fs/msdosfs/msdosfs_vfsops.c
==============================================================================
--- head/sys/fs/msdosfs/msdosfs_vfsops.c	Fri Oct 28 11:34:32 2016	(r308024)
+++ head/sys/fs/msdosfs/msdosfs_vfsops.c	Fri Oct 28 11:35:06 2016	(r308025)
@@ -742,7 +742,7 @@ mountmsdosfs(struct vnode *devvp, struct
 	mp->mnt_stat.f_fsid.val[1] = mp->mnt_vfc->vfc_typenum;
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_USES_BCACHE;
+	mp->mnt_kern_flag |= MNTK_USES_BCACHE | MNTK_NO_IOPF;
 	MNT_IUNLOCK(mp);
 
 	if (pmp->pm_flags & MSDOSFS_LARGEFS)

Modified: head/sys/fs/msdosfs/msdosfs_vnops.c
==============================================================================
--- head/sys/fs/msdosfs/msdosfs_vnops.c	Fri Oct 28 11:34:32 2016	(r308024)
+++ head/sys/fs/msdosfs/msdosfs_vnops.c	Fri Oct 28 11:35:06 2016	(r308025)
@@ -593,7 +593,7 @@ msdosfs_read(struct vop_read_args *ap)
 		diff = blsize - bp->b_resid;
 		if (diff < n)
 			n = diff;
-		error = uiomove(bp->b_data + on, (int) n, uio);
+		error = vn_io_fault_uiomove(bp->b_data + on, (int) n, uio);
 		brelse(bp);
 	} while (error == 0 && uio->uio_resid > 0 && n != 0);
 	if (!isadir && (error == 0 || uio->uio_resid != orig_resid) &&
@@ -723,6 +723,12 @@ msdosfs_write(struct vop_write_args *ap)
 			 * then no need to read data from disk.
 			 */
 			bp = getblk(thisvp, bn, pmp->pm_bpcluster, 0, 0, 0);
+			/*
+			 * This call to vfs_bio_clrbuf() ensures that
+			 * even if vn_io_fault_uiomove() below faults,
+			 * garbage from the newly instantiated buffer
+			 * is not exposed to the userspace via mmap().
+			 */
 			vfs_bio_clrbuf(bp);
 			/*
 			 * Do the bmap now, since pcbmap needs buffers
@@ -760,7 +766,7 @@ msdosfs_write(struct vop_write_args *ap)
 		/*
 		 * Copy the data from user space into the buf header.
 		 */
-		error = uiomove(bp->b_data + croffset, n, uio);
+		error = vn_io_fault_uiomove(bp->b_data + croffset, n, uio);
 		if (error) {
 			brelse(bp);
 			break;

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