linux-kernel - [tip:x86/urgent] Revert "x86/unwind: Detect bad stack return address"

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Date:   Fri, 23 Dec 2016 11:36:48 -0800
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, tglx@...utronix.de,
        dvlasenk@...hat.com, brgerst@...il.com, mingo@...nel.org,
        linux-kernel@...r.kernel.org, andreyknvl@...gle.com,
        luto@...nel.org, mhiramat@...nel.org, peterz@...radead.org,
        bp@...en8.de, jpoimboe@...hat.com, hpa@...or.com
Subject: [tip:x86/urgent] Revert "x86/unwind: Detect bad stack return
 address"

Commit-ID:  c280f7736ab26a601932b1ce017a3840dbedcfdc
Gitweb:     http://git.kernel.org/tip/c280f7736ab26a601932b1ce017a3840dbedcfdc
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Thu, 22 Dec 2016 09:02:49 -0600
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 23 Dec 2016 20:32:30 +0100

Revert "x86/unwind: Detect bad stack return address"

Revert the following commit:

  b6959a362177 ("x86/unwind: Detect bad stack return address")

... because Andrey Konovalov reported an unwinder warning:

  WARNING: unrecognized kernel stack return address ffffffffa0000001 at ffff88006377fa18 in a.out:4467

The unwind was initiated from an interrupt which occurred while running in the
generated code for a kprobe.  The unwinder printed the warning because it
expected regs->ip to point to a valid text address, but instead it pointed to
the generated code.

Eventually we may want come up with a way to identify generated kprobe
code so the unwinder can know that it's a valid return address.  Until
then, just remove the warning.

Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/02f296848fbf49fb72dfeea706413ecbd9d4caf6.1482418739.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/unwind_frame.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 20d4b4e..4443e49 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -51,16 +51,7 @@ unsigned long unwind_get_return_address(struct unwind_state *state)
 	addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, *addr_p,
 				     addr_p);
 
-	if (!__kernel_text_address(addr)) {
-		printk_deferred_once(KERN_WARNING
-			"WARNING: unrecognized kernel stack return address %p at %p in %s:%d\n",
-			(void *)addr, addr_p, state->task->comm,
-			state->task->pid);
-		unwind_dump(state, addr_p);
-		return 0;
-	}
-
-	return addr;
+	return __kernel_text_address(addr) ? addr : 0;
 }
 EXPORT_SYMBOL_GPL(unwind_get_return_address);