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Commit 2e4be0d0 authored by Vernon Lovejoy's avatar Vernon Lovejoy Committed by Josh Poimboeuf
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x86/show_trace_log_lvl: Ensure stack pointer is aligned, again



The commit e335bb51 ("x86/unwind: Ensure stack pointer is aligned")
tried to align the stack pointer in show_trace_log_lvl(), otherwise the
"stack < stack_info.end" check can't guarantee that the last read does
not go past the end of the stack.

However, we have the same problem with the initial value of the stack
pointer, it can also be unaligned. So without this patch this trivial
kernel module

	#include <linux/module.h>

	static int init(void)
	{
		asm volatile("sub    $0x4,%rsp");
		dump_stack();
		asm volatile("add    $0x4,%rsp");

		return -EAGAIN;
	}

	module_init(init);
	MODULE_LICENSE("GPL");

crashes the kernel.

Fixes: e335bb51 ("x86/unwind: Ensure stack pointer is aligned")
Signed-off-by: default avatarVernon Lovejoy <vlovejoy@redhat.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20230512104232.GA10227@redhat.com


Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
parent f7ba52f3
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