The patch below does not apply to the 6.17-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-6.17.y git checkout FETCH_HEAD git cherry-pick -x ea0d55ae4b3207c33691a73da3443b1fd379f1d2 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025102040-gopher-dipping-a96a@gregkh' --subject-prefix 'PATCH 6.17.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From ea0d55ae4b3207c33691a73da3443b1fd379f1d2 Mon Sep 17 00:00:00 2001 From: Ada Couprie Diaz ada.coupriediaz@arm.com Date: Tue, 14 Oct 2025 10:25:36 +0100 Subject: [PATCH] arm64: debug: always unmask interrupts in el0_softstp()

We intend that EL0 exception handlers unmask all DAIF exceptions before calling exit_to_user_mode().

When completing single-step of a suspended breakpoint, we do not call local_daif_restore(DAIF_PROCCTX) before calling exit_to_user_mode(), leaving all DAIF exceptions masked.

When pseudo-NMIs are not in use this is benign.

When pseudo-NMIs are in use, this is unsound. At this point interrupts are masked by both DAIF.IF and PMR_EL1, and subsequent irq flag manipulation may not work correctly. For example, a subsequent local_irq_enable() within exit_to_user_mode_loop() will only unmask interrupts via PMR_EL1 (leaving those masked via DAIF.IF), and anything depending on interrupts being unmasked (e.g. delivery of signals) will not work correctly.

This was detected by CONFIG_ARM64_DEBUG_PRIORITY_MASKING.

Move the call to `try_step_suspended_breakpoints()` outside of the check so that interrupts can be unmasked even if we don't call the step handler.

Fixes: 0ac7584c08ce ("arm64: debug: split single stepping exception entry") Cc: stable@vger.kernel.org # 6.17 Signed-off-by: Ada Couprie Diaz ada.coupriediaz@arm.com Acked-by: Mark Rutland mark.rutland@arm.com [catalin.marinas@arm.com: added Mark's rewritten commit log and some whitespace] Signed-off-by: Catalin Marinas catalin.marinas@arm.com

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index f546a914f041..a9c81715ce59 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -697,6 +697,8 @@ static void noinstr el0_breakpt(struct pt_regs *regs, unsigned long esr)

static void noinstr el0_softstp(struct pt_regs *regs, unsigned long esr) { + bool step_done; + if (!is_ttbr0_addr(regs->pc)) arm64_apply_bp_hardening();

@@ -707,10 +709,10 @@ static void noinstr el0_softstp(struct pt_regs *regs, unsigned long esr) * If we are stepping a suspended breakpoint there's nothing more to do: * the single-step is complete. */ - if (!try_step_suspended_breakpoints(regs)) { - local_daif_restore(DAIF_PROCCTX); + step_done = try_step_suspended_breakpoints(regs); + local_daif_restore(DAIF_PROCCTX); + if (!step_done) do_el0_softstep(esr, regs); - } arm64_exit_to_user_mode(regs); }