kernel: fix f2fs on big endian machines

The WD MyBook Live SquashFS images didn't work anymore due to
a upstream regression in f2fs commit: 0cfe75c5b01199
("f2fs: enhance sanity_check_raw_super() to avoid potential overflows")
that got backported to 4.14.86 and landed in 4.18.

by Martin Blumenstingl:
|Treat "block_count" from struct f2fs_super_block as 64-bit little endian
|value in sanity_check_raw_super() because struct f2fs_super_block
|declares "block_count" as "__le64".
|
|This fixes a bug where the superblock validation fails on big endian
|devices with the following error:
|  F2FS-fs (sda1): Wrong segment_count / block_count (61439 > 0)
|  F2FS-fs (sda1): Can't find valid F2FS filesystem in 1th superblock
|  F2FS-fs (sda1): Wrong segment_count / block_count (61439 > 0)
|  F2FS-fs (sda1): Can't find valid F2FS filesystem in 2th superblock
|As result of this the partition cannot be mounted.
|
|With this patch applied the superblock validation works fine and the
|partition can be mounted again:
|  F2FS-fs (sda1): Mounted with checkpoint version = 7c84
|
|My little endian x86-64 hardware was able to mount the partition without
|this fix.
|To confirm that mounting f2fs filesystems works on big endian machines
|again I tested this on a 32-bit MIPS big endian (lantiq) device.

Hopefully, this will do until Martin's patch moved through upstream
to -stable.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/target/linux/generic/pending-4.14/510-f2fs-fix-sanity_check_raw_super-on-big-endian-machines.patch b/target/linux/generic/pending-4.14/510-f2fs-fix-sanity_check_raw_super-on-big-endian-machines.patch
new file mode 100644
index 0000000000..6cbaf28e81
--- /dev/null
+++ b/target/linux/generic/pending-4.14/510-f2fs-fix-sanity_check_raw_super-on-big-endian-machines.patch
@@ -0,0 +1,51 @@
+From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+To: linux-f2fs-devel@lists.sourceforge.net, yuchao0@huawei.com,
+        jaegeuk@kernel.org
+Subject: [PATCH v2 1/1] f2fs: fix validation of the block count in
+ sanity_check_raw_super
+Date: Sat, 22 Dec 2018 11:22:26 +0100
+Message-Id: <20181222102226.10050-2-martin.blumenstingl@googlemail.com>
+
+Treat "block_count" from struct f2fs_super_block as 64-bit little endian
+value in sanity_check_raw_super() because struct f2fs_super_block
+declares "block_count" as "__le64".
+
+This fixes a bug where the superblock validation fails on big endian
+devices with the following error:
+  F2FS-fs (sda1): Wrong segment_count / block_count (61439 > 0)
+  F2FS-fs (sda1): Can't find valid F2FS filesystem in 1th superblock
+  F2FS-fs (sda1): Wrong segment_count / block_count (61439 > 0)
+  F2FS-fs (sda1): Can't find valid F2FS filesystem in 2th superblock
+As result of this the partition cannot be mounted.
+
+With this patch applied the superblock validation works fine and the
+partition can be mounted again:
+  F2FS-fs (sda1): Mounted with checkpoint version = 7c84
+
+My little endian x86-64 hardware was able to mount the partition without
+this fix.
+To confirm that mounting f2fs filesystems works on big endian machines
+again I tested this on a 32-bit MIPS big endian (lantiq) device.
+
+Fixes: 0cfe75c5b01199 ("f2fs: enhance sanity_check_raw_super() to avoid potential overflows")
+Cc: stable@vger.kernel.org
+Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+Reviewed-by: Chao Yu <yuchao0@huawei.com>
+---
+
+--- a/fs/f2fs/super.c
++++ b/fs/f2fs/super.c
+@@ -1897,10 +1897,10 @@ static int sanity_check_raw_super(struct
+ 		return 1;
+ 	}
+ 
+-	if (segment_count > (le32_to_cpu(raw_super->block_count) >> 9)) {
++	if (segment_count > (le64_to_cpu(raw_super->block_count) >> 9)) {
+ 		f2fs_msg(sb, KERN_INFO,
+-			"Wrong segment_count / block_count (%u > %u)",
+-			segment_count, le32_to_cpu(raw_super->block_count));
++			"Wrong segment_count / block_count (%u > %llu)",
++			segment_count, le64_to_cpu(raw_super->block_count));
+ 		return 1;
+ 	}
+