The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x d35652a5fc9944784f6f50a5c979518ff8dacf61 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023101547-captivate-regress-4cb0@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

d35652a5fc99 ("x86/alternatives: Disable KASAN in apply_alternatives()") 6becb5026b81 ("x86/alternative: Make debug-alternative selective") ac0ee0a9560c ("x86/alternatives: Teach text_poke_bp() to patch Jcc.d32 instructions") 5d1dd961e743 ("x86/alternatives: Add alt_instr.flags") 931ab63664f0 ("x86/ibt: Implement FineIBT") b341b20d648b ("x86: Add prefix symbols for function padding") 3b6c1747da48 ("x86/retpoline: Add SKL retthunk retpolines") 52354973573c ("x86/asm: Provide ALTERNATIVE_3") eaf44c816ed8 ("x86/modules: Add call patching") e81dc127ef69 ("x86/callthunks: Add call patching for call depth tracking") 80e4c1cd42ff ("x86/retbleed: Add X86_FEATURE_CALL_DEPTH") bea75b33895f ("x86/Kconfig: Introduce function padding") 8f7c0d8b23c3 ("x86/Kconfig: Add CONFIG_CALL_THUNKS") 8eb5d34e77c6 ("x86/asm: Differentiate between code and function alignment") d49a0626216b ("arch: Introduce CONFIG_FUNCTION_ALIGNMENT")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d35652a5fc9944784f6f50a5c979518ff8dacf61 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Date: Thu, 12 Oct 2023 13:04:24 +0300 Subject: [PATCH] x86/alternatives: Disable KASAN in apply_alternatives()

Fei has reported that KASAN triggers during apply_alternatives() on a 5-level paging machine:

BUG: KASAN: out-of-bounds in rcu_is_watching() Read of size 4 at addr ff110003ee6419a0 by task swapper/0/0 ... __asan_load4() rcu_is_watching() trace_hardirqs_on() text_poke_early() apply_alternatives() ...

On machines with 5-level paging, cpu_feature_enabled(X86_FEATURE_LA57) gets patched. It includes KASAN code, where KASAN_SHADOW_START depends on __VIRTUAL_MASK_SHIFT, which is defined with cpu_feature_enabled().

KASAN gets confused when apply_alternatives() patches the KASAN_SHADOW_START users. A test patch that makes KASAN_SHADOW_START static, by replacing __VIRTUAL_MASK_SHIFT with 56, works around the issue.

Fix it for real by disabling KASAN while the kernel is patching alternatives.

[ mingo: updated the changelog ]

Fixes: 6657fca06e3f ("x86/mm: Allow to boot without LA57 if CONFIG_X86_5LEVEL=y") Reported-by: Fei Yang fei.yang@intel.com Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Ingo Molnar mingo@kernel.org Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20231012100424.1456-1-kirill.shutemov@linux.intel....

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 517ee01503be..73be3931e4f0 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -403,6 +403,17 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start, u8 insn_buff[MAX_PATCH_LEN];

DPRINTK(ALT, "alt table %px, -> %px", start, end); + + /* + * In the case CONFIG_X86_5LEVEL=y, KASAN_SHADOW_START is defined using + * cpu_feature_enabled(X86_FEATURE_LA57) and is therefore patched here. + * During the process, KASAN becomes confused seeing partial LA57 + * conversion and triggers a false-positive out-of-bound report. + * + * Disable KASAN until the patching is complete. + */ + kasan_disable_current(); + /* * The scan order should be from start to end. A later scanned * alternative code can overwrite previously scanned alternative code. @@ -452,6 +463,8 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start,

text_poke_early(instr, insn_buff, insn_buff_sz); } + + kasan_enable_current(); }

static inline bool is_jcc32(struct insn *insn)