[nacked] ubsan-dont-handle-misaligned-address-when-support-unaligned-access.patch removed from -mm tree

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The patch titled
     Subject: lib/ubsan.c: don't handle misaligned address when kernel supports unaligned access
has been removed from the -mm tree.  Its filename was
     ubsan-dont-handle-misaligned-address-when-support-unaligned-access.patch

This patch was dropped because it was nacked

------------------------------------------------------
From: Ding Tianhong <dingtianhong@xxxxxxxxxx>
Subject: lib/ubsan.c: don't handle misaligned address when kernel supports unaligned access

ubsan reports a warning like:

UBSAN: Undefined behaviour in ../include/linux/etherdevice.h:386:9
load of misaligned address ffffffc069ba0482 for type 'long unsigned int'
which requires 8 byte alignment
CPU: 0 PID: 901 Comm: sshd Not tainted 4.xx+ #1
Hardware name: linux,dummy-virt (DT)
Call trace:
[<ffffffc000093600>] dump_backtrace+0x0/0x348
[<ffffffc000093968>] show_stack+0x20/0x30
[<ffffffc001651664>] dump_stack+0x144/0x1b4
[<ffffffc0016519b0>] ubsan_epilogue+0x18/0x74
[<ffffffc001651bac>] __ubsan_handle_type_mismatch+0x1a0/0x25c
[<ffffffc00125d8a0>] dev_gro_receive+0x17d8/0x1830
[<ffffffc00125d928>] napi_gro_receive+0x30/0x158
[<ffffffc000f4f93c>] virtnet_receive+0xad4/0x1fa8

The reason is that when enabling the CONFIG_UBSAN_ALIGNMENT, ubsan will
report the unaligned access even if the system supports it
(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y).  This produces a lot of noise
in the log and causes confusion.

Prevent the detection of unaligned access when the system support
unaligned access.

[dingtianhong@xxxxxxxxxx: add braces around if block]
Link: http://lkml.kernel.org/r/5b905d56-609e-3822-096a-3b93b3eb7675@xxxxxxxxxx
Signed-off-by: Ding Tianhong <dingtianhong@xxxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 lib/ubsan.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff -puN lib/ubsan.c~ubsan-dont-handle-misaligned-address-when-support-unaligned-access lib/ubsan.c
--- a/lib/ubsan.c~ubsan-dont-handle-misaligned-address-when-support-unaligned-access
+++ a/lib/ubsan.c
@@ -321,9 +321,10 @@ void __ubsan_handle_type_mismatch(struct
 
 	if (!ptr)
 		handle_null_ptr_deref(data);
-	else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
-		handle_missaligned_access(data, ptr);
-	else
+	else if (data->alignment && !IS_ALIGNED(ptr, data->alignment)) {
+		if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+			handle_missaligned_access(data, ptr);
+	} else
 		handle_object_size_mismatch(data, ptr);
 }
 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
_

Patches currently in -mm which might be from dingtianhong@xxxxxxxxxx are


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