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* [PATCH v4] x86/insn, tools/x86: Fix some potential undefined behavior.
@ 2021-09-23 16:18 Ian Rogers
  2021-09-24 10:45 ` [tip: x86/urgent] x86/insn, tools/x86: Fix undefined behavior due to potential unaligned accesses tip-bot2 for Numfor Mbiziwo-Tiapo
                   ` (2 more replies)
  0 siblings, 3 replies; 8+ messages in thread
From: Ian Rogers @ 2021-09-23 16:18 UTC (permalink / raw)
  To: Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
	H. Peter Anvin, Peter Zijlstra (Intel), Masami Hiramatsu,
	Josh Poimboeuf, linux-kernel, Adrian Hunter,
	Arnaldo Carvalho de Melo, David Laight
  Cc: Numfor Mbiziwo-Tiapo, Ian Rogers

From: Numfor Mbiziwo-Tiapo <nums@google.com>

Don't perform unaligned loads in __get_next and __peek_nbyte_next as
these are forms of undefined behavior.

These problems were identified using the undefined behavior sanitizer
(ubsan) with the tools version of the code and perf test. Part of this
patch was previously posted here:
https://lore.kernel.org/lkml/20190724184512.162887-4-nums@google.com/

v4. Fixes a typo.

v3. Is a rebase picking up a fix for big endian architectures.

v2. removes the validate_next check and merges the 2 changes into one as
requested by Masami Hiramatsu <mhiramat@kernel.org>

Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/x86/lib/insn.c       | 4 ++--
 tools/arch/x86/lib/insn.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
index 058f19b20465..c565def611e2 100644
--- a/arch/x86/lib/insn.c
+++ b/arch/x86/lib/insn.c
@@ -37,10 +37,10 @@
 	((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)
 
 #define __get_next(t, insn)	\
-	({ t r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); leXX_to_cpu(t, r); })
+	({ t r; memcpy(&r, insn->next_byte, sizeof(t)); insn->next_byte += sizeof(t); leXX_to_cpu(t, r); })
 
 #define __peek_nbyte_next(t, insn, n)	\
-	({ t r = *(t*)((insn)->next_byte + n); leXX_to_cpu(t, r); })
+	({ t r; memcpy(&r, (insn)->next_byte + n, sizeof(t)); leXX_to_cpu(t, r); })
 
 #define get_next(t, insn)	\
 	({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t, insn); })
diff --git a/tools/arch/x86/lib/insn.c b/tools/arch/x86/lib/insn.c
index c41f95815480..797699462cd8 100644
--- a/tools/arch/x86/lib/insn.c
+++ b/tools/arch/x86/lib/insn.c
@@ -37,10 +37,10 @@
 	((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)
 
 #define __get_next(t, insn)	\
-	({ t r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); leXX_to_cpu(t, r); })
+	({ t r; memcpy(&r, insn->next_byte, sizeof(t)); insn->next_byte += sizeof(t); leXX_to_cpu(t, r); })
 
 #define __peek_nbyte_next(t, insn, n)	\
-	({ t r = *(t*)((insn)->next_byte + n); leXX_to_cpu(t, r); })
+	({ t r; memcpy(&r, (insn)->next_byte + n, sizeof(t)); leXX_to_cpu(t, r); })
 
 #define get_next(t, insn)	\
 	({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t, insn); })
-- 
2.33.0.464.g1972c5931b-goog


^ permalink raw reply related	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2021-09-27 12:33 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2021-09-23 16:18 [PATCH v4] x86/insn, tools/x86: Fix some potential undefined behavior Ian Rogers
2021-09-24 10:45 ` [tip: x86/urgent] x86/insn, tools/x86: Fix undefined behavior due to potential unaligned accesses tip-bot2 for Numfor Mbiziwo-Tiapo
2021-09-24 19:02 ` [PATCH v4] x86/insn, tools/x86: Fix some potential undefined behavior Arnaldo Carvalho de Melo
2021-09-25  4:39   ` Masami Hiramatsu
2021-09-26 11:59     ` Arnaldo Carvalho de Melo
2021-09-26 15:25       ` Borislav Petkov
2021-09-27 12:33         ` Arnaldo Carvalho de Melo
2021-09-27  7:36 ` H. Peter Anvin

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