[PATCH 1/1] Revert "iomap: fall back to buffered writes for invalidation failures"

Lee Jones
2022-02-09T08:53:40Z

This reverts commit 60263d5889e6dc5987dc51b801be4955ff2e4aa7.

Reverting since this commit opens a potential avenue for abuse.

The C-reproducer and more information can be found at the link below.

With this patch applied, I can no longer get the repro to trigger.

kernel BUG at fs/ext4/inode.c:2647!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 459 Comm: syz-executor359 Tainted: G W 5.10.93-syzkaller-01028-g0347b1658399 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:mpage_prepare_extent_to_map+0xbe9/0xc00 fs/ext4/inode.c:2647
Code: e8 fc bd c3 ff e9 80 f6 ff ff 44 89 e9 80 e1 07 38 c1 0f 8c a6 fe ff ff 4c 89 ef e8 e1 bd c3 ff e9 99 fe ff ff e8 87 c9 89 ff <0f> 0b e8 80 c9 89 ff 0f 0b e8 79 1e b8 02 66 0f 1f 84 00 00 00 00
RSP: 0018:ffffc90000e2e9c0 EFLAGS: 00010293
RAX: ffffffff81e321f9 RBX: 0000000000000000 RCX: ffff88810c12cf00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000e2eb90 R08: ffffffff81e31e71 R09: fffff940008d68b1
R10: fffff940008d68b1 R11: 0000000000000000 R12: ffffea00046b4580
R13: ffffc90000e2ea80 R14: 000000000000011e R15: dffffc0000000000
FS: 00007fcfd0717700(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fcfd07d5520 CR3: 000000010a142000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
ext4_writepages+0xcbb/0x3950 fs/ext4/inode.c:2776
do_writepages+0x13a/0x280 mm/page-writeback.c:2358
__filemap_fdatawrite_range+0x356/0x420 mm/filemap.c:427
filemap_write_and_wait_range+0x64/0xe0 mm/filemap.c:660
__iomap_dio_rw+0x621/0x10c0 fs/iomap/direct-io.c:495
iomap_dio_rw+0x35/0x80 fs/iomap/direct-io.c:611
ext4_dio_write_iter fs/ext4/file.c:571 [inline]
ext4_file_write_iter+0xfc5/0x1b70 fs/ext4/file.c:681
do_iter_readv_writev+0x548/0x740 include/linux/fs.h:1941
do_iter_write+0x182/0x660 fs/read_write.c:866
vfs_iter_write+0x7c/0xa0 fs/read_write.c:907
iter_file_splice_write+0x7fb/0xf70 fs/splice.c:686
do_splice_from fs/splice.c:764 [inline]
direct_splice_actor+0xfe/0x130 fs/splice.c:933
splice_direct_to_actor+0x4f4/0xbc0 fs/splice.c:888
do_splice_direct+0x28b/0x3e0 fs/splice.c:976
do_sendfile+0x914/0x1390 fs/read_write.c:1257

Link: https://syzkaller.appspot.com/bug?extid=41c966bf0729a530bd8d

From the patch:
Cc: Stable <stable@vger.kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Theodore Ts'o <tytso@mit.edu> # for ext4
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Ritesh Harjani <riteshh@linux.ibm.com>

Others:
Cc: Johannes Thumshirn <jth@kernel.org>
Cc: linux-xfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-ext4@vger.kernel.org
Cc: cluster-devel@redhat.com

Fixes: 60263d5889e6d ("iomap: fall back to buffered writes for invalidation failures")
Reported-by: syzbot+0ed9f769264276638893@syzkaller.appspotmail.com
Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
fs/ext4/file.c | 2 --
fs/gfs2/file.c | 3 +--
fs/iomap/direct-io.c | 16 +++++-----------
fs/iomap/trace.h | 1 -
fs/xfs/xfs_file.c | 4 ++--
fs/zonefs/super.c | 7 ++-----
6 files changed, 10 insertions(+), 23 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 3ed8c048fb12c..cb347c3b35535 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -551,8 +551,6 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
iomap_ops = &ext4_iomap_overwrite_ops;
ret = iomap_dio_rw(iocb, from, iomap_ops, &ext4_dio_write_ops,
is_sync_kiocb(iocb) || unaligned_io || extend);
- if (ret == -ENOTBLK)
- ret = 0;

if (extend)
ret = ext4_handle_inode_extension(inode, offset, ret, count);
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index b39b339feddc9..847adb97380d3 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -835,8 +835,7 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,

ret = iomap_dio_rw(iocb, from, &gfs2_iomap_ops, NULL,
is_sync_kiocb(iocb));
- if (ret == -ENOTBLK)
- ret = 0;
+
out:
gfs2_glock_dq(gh);
out_uninit:
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 933f234d5becd..ddcd06c0c452d 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -10,7 +10,6 @@
#include <linux/backing-dev.h>
#include <linux/uio.h>
#include <linux/task_io_accounting_ops.h>
-#include "trace.h"

#include "../internal.h"

@@ -413,9 +412,6 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
* can be mapped into multiple disjoint IOs and only a subset of the IOs issued
* may be pure data writes. In that case, we still need to do a full data sync
* completion.
- *
- * Returns -ENOTBLK In case of a page invalidation invalidation failure for
- * writes. The callers needs to fall back to buffered I/O in this case.
*/
struct iomap_dio *
__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
@@ -493,15 +489,13 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
if (iov_iter_rw(iter) == WRITE) {
/*
* Try to invalidate cache pages for the range we are writing.
- * If this invalidation fails, let the caller fall back to
- * buffered I/O.
+ * If this invalidation fails, tough, the write will still work,
+ * but racing two incompatible write paths is a pretty crazy
+ * thing to do, so we don't support it 100%.
*/
if (invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
- end >> PAGE_SHIFT)) {
- trace_iomap_dio_invalidate_fail(inode, pos, count);
- ret = -ENOTBLK;
- goto out_free_dio;
- }
+ end >> PAGE_SHIFT))
+ dio_warn_stale_pagecache(iocb->ki_filp);

if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
ret = sb_init_dio_done_wq(inode->i_sb);
diff --git a/fs/iomap/trace.h b/fs/iomap/trace.h
index fdc7ae388476f..5693a39d52fb6 100644
--- a/fs/iomap/trace.h
+++ b/fs/iomap/trace.h
@@ -74,7 +74,6 @@ DEFINE_EVENT(iomap_range_class, name, \
DEFINE_RANGE_EVENT(iomap_writepage);
DEFINE_RANGE_EVENT(iomap_releasepage);
DEFINE_RANGE_EVENT(iomap_invalidatepage);
-DEFINE_RANGE_EVENT(iomap_dio_invalidate_fail);

#define IOMAP_TYPE_STRINGS \
{ IOMAP_HOLE, "HOLE" }, \
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 5b0f93f738372..43e2c057214d9 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -589,8 +589,8 @@ xfs_file_dio_aio_write(
xfs_iunlock(ip, iolock);

/*
- * No fallback to buffered IO after short writes for XFS, direct I/O
- * will either complete fully or return an error.
+ * No fallback to buffered IO on errors for XFS, direct IO will either
+ * complete fully or fail.
*/
ASSERT(ret < 0 || ret == count);
return ret;
diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index bec47f2d074be..d54fbef3db4df 100644
--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -851,11 +851,8 @@ static ssize_t zonefs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
if (iocb->ki_pos >= ZONEFS_I(inode)->i_max_size)
return -EFBIG;

- if (iocb->ki_flags & IOCB_DIRECT) {
- ssize_t ret = zonefs_file_dio_write(iocb, from);
- if (ret != -ENOTBLK)
- return ret;
- }
+ if (iocb->ki_flags & IOCB_DIRECT)
+ return zonefs_file_dio_write(iocb, from);

return zonefs_file_buffered_write(iocb, from);
}
--
2.35.0.263.gb82422642f-goog