From: Vernon Lovejoy vlovejoy@redhat.com
commit 2e4be0d011f21593c6b316806779ba1eba2cd7e0 upstream.
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 Link: https://lore.kernel.org/r/20230512104232.GA10227@redhat.com Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/dumpstack.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -195,7 +195,6 @@ void show_trace_log_lvl(struct task_stru printk("%sCall Trace:\n", log_lvl);
unwind_start(&state, task, regs, stack); - stack = stack ? : get_stack_pointer(task, regs); regs = unwind_get_entry_regs(&state, &partial);
/* @@ -214,9 +213,13 @@ void show_trace_log_lvl(struct task_stru * - hardirq stack * - entry stack */ - for ( ; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { + for (stack = stack ?: get_stack_pointer(task, regs); + stack; + stack = stack_info.next_sp) { const char *stack_name;
+ stack = PTR_ALIGN(stack, sizeof(long)); + if (get_stack_info(stack, task, &stack_info, &visit_mask)) { /* * We weren't on a valid stack. It's possible that