This is a note to let you know that I've just added the patch titled x86/insn, tools/x86: Fix undefined behavior due to potential unaligned accesses to the 5.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-insn-tools-x86-fix-undefined-behavior-due-to-pot.patch and it can be found in the queue-5.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit d7f21698e56c5154e55baf991702fce94ca35bd1 Author: Numfor Mbiziwo-Tiapo <nums@xxxxxxxxxx> Date: Thu Sep 23 09:18:43 2021 -0700 x86/insn, tools/x86: Fix undefined behavior due to potential unaligned accesses [ Upstream commit 5ba1071f7554c4027bdbd712a146111de57918de ] Don't perform unaligned loads in __get_next() and __peek_nbyte_next() as these are forms of undefined behavior: "A pointer to an object or incomplete type may be converted to a pointer to a different object or incomplete type. If the resulting pointer is not correctly aligned for the pointed-to type, the behavior is undefined." (from http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf) These problems were identified using the undefined behavior sanitizer (ubsan) with the tools version of the code and perf test. [ bp: Massage commit message. ] Signed-off-by: Numfor Mbiziwo-Tiapo <nums@xxxxxxxxxx> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20210923161843.751834-1-irogers@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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); })