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[PATCH 4.3 153/157] direct-io: Fix negative return from dio read beyond eof

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4.3-stable review patch.  If anyone has any objections, please let me know.

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

From: Jan Kara <jack@suse.cz>

commit 74cedf9b6c603f2278a05bc91b140b32b434d0b5 upstream.

Assume a filesystem with 4KB blocks. When a file has size 1000 bytes and
we issue direct IO read at offset 1024, blockdev_direct_IO() reads the
tail of the last block and the logic for handling short DIO reads in
dio_complete() results in a return value -24 (1000 - 1024) which
obviously confuses userspace.

Fix the problem by bailing out early once we sample i_size and can
reliably check that direct IO read starts beyond i_size.

Reported-by: Avi Kivity <avi@scylladb.com>
Fixes: 9fe55eea7e4b444bafc42fa0000cc2d1d2847275
CC: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/direct-io.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1161,6 +1161,15 @@ do_blockdev_direct_IO(struct kiocb *iocb
 		}
 	}
 
+	/* Once we sampled i_size check for reads beyond EOF */
+	dio->i_size = i_size_read(inode);
+	if (iov_iter_rw(iter) == READ && offset >= dio->i_size) {
+		if (dio->flags & DIO_LOCKING)
+			mutex_unlock(&inode->i_mutex);
+		kmem_cache_free(dio_cache, dio);
+		goto out;
+	}
+
 	/*
 	 * For file extending writes updating i_size before data writeouts
 	 * complete can expose uninitialized blocks in dumb filesystems.
@@ -1214,7 +1223,6 @@ do_blockdev_direct_IO(struct kiocb *iocb
 	sdio.next_block_for_io = -1;
 
 	dio->iocb = iocb;
-	dio->i_size = i_size_read(inode);
 
 	spin_lock_init(&dio->bio_lock);
 	dio->refcount = 1;

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[PATCH 4.3 000/157] 4.3.5-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 001/157] x86 smpboot: Re-enable init_udelay=0 by default on modern CPUs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
    Re: [PATCH 4.3 001/157] x86 smpboot: Re-enable init_udelay=0 by  default on modern CPUs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 23:30 +0100
    Re: [PATCH 4.3 001/157] x86 smpboot: Re-enable init_udelay=0 by  default on modern CPUs Donald Parsons <dparsons@brightdsl.net> - 2016-01-27 23:30 +0100
  [PATCH 4.3 052/157] ALSA: seq: Fix race at timer setup and close Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 046/157] ALSA: hda - Add mic mute hotkey quirk for Lenovo ThinkCentre AIO Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 010/157] KVM: svm: unconditionally intercept #DB Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 155/157] mn10300: Select CONFIG_HAVE_UID16 to fix build failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 154/157] fix the regression from "direct-io: Fix negative return from dio read beyond eof" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:20 +0100
  [PATCH 4.3 126/157] powerpc/opal-irqchip: Fix deadlock introduced by "Fix double endian conversion" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:20 +0100
  [PATCH 4.3 135/157] arm64: cmpxchg_dbl: fix return value type Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:20 +0100
  [PATCH 4.3 134/157] arm64: bpf: fix mod-by-zero case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:20 +0100
  [PATCH 4.3 044/157] ALSA: hda - Set SKL+ hda controller power at freeze() and thaw() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 128/157] powerpc: Make value-returning atomics fully ordered Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 157/157] arm64: KVM: Add workaround for Cortex-A57 erratum 834220 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 131/157] powerpc/module: Handle R_PPC64_ENTRY relocations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 129/157] powerpc: Make {cmp}xchg* and their atomic_ versions fully ordered Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 133/157] arm64: bpf: fix div-by-zero case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 156/157] arm64: restore bogomips information in /proc/cpuinfo Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 147/157] parisc iommu: fix panic due to trying to allocate too large region Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 132/157] recordmcount: arm64: Replace the ignored mcount call into nop Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 148/157] HID: wacom: Tie cached HID_DG_CONTACTCOUNT indices to report ID Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 150/157] HID: core: Avoid uninitialized buffer access Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 149/157] HID: wacom: Expect touch_max touches if HID_DG_CONTACTCOUNT not present Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 130/157] scripts/recordmcount.pl: support data in text section on powerpc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 153/157] direct-io: Fix negative return from dio read beyond eof Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  Re: [PATCH 4.3 000/157] 4.3.5-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-01-28 00:30 +0100
  Re: [PATCH 4.3 000/157] 4.3.5-stable review Guenter Roeck <linux@roeck-us.net> - 2016-01-28 03:20 +0100

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