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From a41537e69b4aa43f0fea02498c2595a81267383b Mon Sep 17 00:00:00 2001
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From: Dmitry Monakhov <dmonakhov@openvz.org>
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Date: Thu, 30 Oct 2014 10:53:16 -0400
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Subject: [PATCH] ext4: prevent bugon on race between write/fcntl
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O_DIRECT flags can be toggeled via fcntl(F_SETFL). But this value checked
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twice inside ext4_file_write_iter() and __generic_file_write() which
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result in BUG_ON inside ext4_direct_IO.
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Let's initialize iocb->private unconditionally.
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TESTCASE: xfstest:generic/036 https://patchwork.ozlabs.org/patch/402445/
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#TYPICAL STACK TRACE:
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kernel BUG at fs/ext4/inode.c:2960!
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invalid opcode: 0000 [#1] SMP
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Modules linked in: brd iTCO_wdt lpc_ich mfd_core igb ptp dm_mirror dm_region_hash dm_log dm_mod
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CPU: 6 PID: 5505 Comm: aio-dio-fcntl-r Not tainted 3.17.0-rc2-00176-gff5c017 #161
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Hardware name: Intel Corporation W2600CR/W2600CR, BIOS SE5C600.86B.99.99.x028.061320111235 06/13/2011
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task: ffff88080e95a7c0 ti: ffff88080f908000 task.ti: ffff88080f908000
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RIP: 0010:[<ffffffff811fabf2>] [<ffffffff811fabf2>] ext4_direct_IO+0x162/0x3d0
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RSP: 0018:ffff88080f90bb58 EFLAGS: 00010246
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RAX: 0000000000000400 RBX: ffff88080fdb2a28 RCX: 00000000a802c818
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RDX: 0000040000080000 RSI: ffff88080d8aeb80 RDI: 0000000000000001
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RBP: ffff88080f90bbc8 R08: 0000000000000000 R09: 0000000000001581
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R10: 0000000000000000 R11: 0000000000000000 R12: ffff88080d8aeb80
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R13: ffff88080f90bbf8 R14: ffff88080fdb28c8 R15: ffff88080fdb2a28
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FS: 00007f23b2055700(0000) GS:ffff880818400000(0000) knlGS:0000000000000000
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CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
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CR2: 00007f23b2045000 CR3: 000000080cedf000 CR4: 00000000000407e0
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Stack:
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ffff88080f90bb98 0000000000000000 7ffffffffffffffe ffff88080fdb2c30
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0000000000000200 0000000000000200 0000000000000001 0000000000000200
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ffff88080f90bbc8 ffff88080fdb2c30 ffff88080f90be08 0000000000000200
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Call Trace:
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[<ffffffff8112ca9d>] generic_file_direct_write+0xed/0x180
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[<ffffffff8112f2b2>] __generic_file_write_iter+0x222/0x370
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[<ffffffff811f495b>] ext4_file_write_iter+0x34b/0x400
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[<ffffffff811bd709>] ? aio_run_iocb+0x239/0x410
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[<ffffffff811bd709>] ? aio_run_iocb+0x239/0x410
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[<ffffffff810990e5>] ? local_clock+0x25/0x30
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[<ffffffff810abd94>] ? __lock_acquire+0x274/0x700
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[<ffffffff811f4610>] ? ext4_unwritten_wait+0xb0/0xb0
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[<ffffffff811bd756>] aio_run_iocb+0x286/0x410
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[<ffffffff810990e5>] ? local_clock+0x25/0x30
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[<ffffffff810ac359>] ? lock_release_holdtime+0x29/0x190
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[<ffffffff811bc05b>] ? lookup_ioctx+0x4b/0xf0
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[<ffffffff811bde3b>] do_io_submit+0x55b/0x740
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[<ffffffff811bdcaa>] ? do_io_submit+0x3ca/0x740
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[<ffffffff811be030>] SyS_io_submit+0x10/0x20
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[<ffffffff815ce192>] system_call_fastpath+0x16/0x1b
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Code: 01 48 8b 80 f0 01 00 00 48 8b 18 49 8b 45 10 0f 85 f1 01 00 00 48 03 45 c8 48 3b 43 48 0f 8f e3 01 00 00 49 83 7c
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24 18 00 75 04 <0f> 0b eb fe f0 ff 83 ec 01 00 00 49 8b 44 24 18 8b 00 85 c0 89
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RIP [<ffffffff811fabf2>] ext4_direct_IO+0x162/0x3d0
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RSP <ffff88080f90bb58>
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Reported-by: Sasha Levin <sasha.levin@oracle.com>
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Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
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Cc: stable@vger.kernel.org
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---
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fs/ext4/file.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/fs/ext4/file.c b/fs/ext4/file.c
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index aca7b24a4432..8131be8c0af3 100644
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--- a/fs/ext4/file.c
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+++ b/fs/ext4/file.c
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@@ -137,10 +137,10 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
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iov_iter_truncate(from, sbi->s_bitmap_maxbytes - pos);
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}
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+ iocb->private = &overwrite;
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if (o_direct) {
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blk_start_plug(&plug;;
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- iocb->private = &overwrite;
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/* check whether we do a DIO overwrite or not */
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if (ext4_should_dioread_nolock(inode) && !aio_mutex &&
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--
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2.1.0
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