Messages in this thread Patch in this message | | | Date | Thu, 27 Apr 2023 16:00:54 +0200 | From | Oleg Nesterov <> | Subject | [PATCH] x86/show_trace_log_lvl: ensure stack pointer is aligned, again |
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From: Vernon Lovejoy <vlovejoy@redhat.com>
The commit e335bb51cc15 ("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: e335bb51cc15 ("x86/unwind: Ensure stack pointer is aligned") Signed-off-by: Vernon Lovejoy <vlovejoy@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- arch/x86/kernel/dumpstack.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 0bf6779187dd..71ab445a29c3 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -214,6 +214,7 @@ static void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, * - hardirq stack * - entry stack */ + stack = PTR_ALIGN(stack, sizeof(long)); for ( ; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { const char *stack_name; -- 2.25.1.362.g51ebf55
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