linux-kernel - [PATCH bpf 1/4] ARM: unwind: Initialize the lr_addr field of unwind_ctrl

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Date:   Tue,  5 Apr 2022 18:33:47 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Alexei Starovoitov <ast@...nel.org>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Shubham Bansal <illusionist.neo@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>, bpf@...r.kernel.org,
        kernel-team@...com, Jiri Olsa <jolsa@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH bpf 1/4] ARM: unwind: Initialize the lr_addr field of unwind_ctrl_block

Since the unwind_ctrl_block::lr_addr is finally passed to
stackframe::lr_addr, that value will be exposed unconditionally.
Thus it should be initialized.

Without this fix, when unwind_frame() doesn't update the
unwind_ctrl_block::lr_addr (e.g. 'lr' register is not saved in the
target function), stackframe::lr_addr will contain a wrong value.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 arch/arm/kernel/unwind.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index a37ea6c772cd..93e767682cf4 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -404,6 +404,7 @@ int unwind_frame(struct stackframe *frame)
 	ctrl.vrs[SP] = frame->sp;
 	ctrl.vrs[LR] = frame->lr;
 	ctrl.vrs[PC] = 0;
+	ctrl.lr_addr = 0;
 
 	if (idx->insn == 1)
 		/* can't unwind */