Commit fbe0d451 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'x86-urgent-2020-07-25' of... 

Merge tag 'x86-urgent-2020-07-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into master

Pull x86 fixes from Ingo Molnar:
 "Misc fixes:

   - Fix a section end page alignment assumption that was causing
     crashes

   - Fix ORC unwinding on freshly forked tasks which haven't executed
     yet and which have empty user task stacks

   - Fix the debug.exception-trace=1 sysctl dumping of user stacks,
     which was broken by recent maccess changes"

* tag 'x86-urgent-2020-07-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/dumpstack: Dump user space code correctly again
  x86/stacktrace: Fix reliable check for empty user task stacks
  x86/unwind/orc: Fix ORC for newly forked tasks
  x86, vmlinux.lds: Page-align end of ..page_aligned sections
parents 78b1afe2 d181d2da

arch/x86/kernel/dumpstack.c

+17 −10
Original line number Diff line number Diff line
@@ -71,6 +71,22 @@ static void printk_stack_address(unsigned long address, int reliable, 
	printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address);

}



static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src,

		     unsigned int nbytes)

{

	if (!user_mode(regs))

		return copy_from_kernel_nofault(buf, (u8 *)src, nbytes);



	/*

	 * Make sure userspace isn't trying to trick us into dumping kernel

	 * memory by pointing the userspace instruction pointer at it.

	 */

	if (__chk_range_not_ok(src, nbytes, TASK_SIZE_MAX))

		return -EINVAL;



	return copy_from_user_nmi(buf, (void __user *)src, nbytes);

}



/*

 * There are a couple of reasons for the 2/3rd prologue, courtesy of Linus:

 *
@@ -97,17 +113,8 @@ void show_opcodes(struct pt_regs *regs, const char *loglvl) 
#define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE)

	u8 opcodes[OPCODE_BUFSIZE];

	unsigned long prologue = regs->ip - PROLOGUE_SIZE;

	bool bad_ip;



	/*

	 * Make sure userspace isn't trying to trick us into dumping kernel

	 * memory by pointing the userspace instruction pointer at it.

	 */

	bad_ip = user_mode(regs) &&

		__chk_range_not_ok(prologue, OPCODE_BUFSIZE, TASK_SIZE_MAX);



	if (bad_ip || copy_from_kernel_nofault(opcodes, (u8 *)prologue,

					OPCODE_BUFSIZE)) {

	if (copy_code(regs, opcodes, prologue, sizeof(opcodes))) {

		printk("%sCode: Bad RIP value.\n", loglvl);

	} else {

		printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %"

arch/x86/kernel/stacktrace.c

+0 −5
Original line number Diff line number Diff line
@@ -58,7 +58,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, 
			 * or a page fault), which can make frame pointers

			 * unreliable.

			 */



			if (IS_ENABLED(CONFIG_FRAME_POINTER))

				return -EINVAL;

		}
@@ -81,10 +80,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, 
	if (unwind_error(&state))

		return -EINVAL;



	/* Success path for non-user tasks, i.e. kthreads and idle tasks */

	if (!(task->flags & (PF_KTHREAD | PF_IDLE)))

		return -EINVAL;



	return 0;

}

arch/x86/kernel/unwind_orc.c

+6 −2
Original line number Diff line number Diff line
@@ -440,8 +440,11 @@ bool unwind_next_frame(struct unwind_state *state) 
	/*

	 * Find the orc_entry associated with the text address.

	 *

	 * Decrement call return addresses by one so they work for sibling

	 * calls and calls to noreturn functions.

	 * For a call frame (as opposed to a signal frame), state->ip points to

	 * the instruction after the call.  That instruction's stack layout

	 * could be different from the call instruction's layout, for example

	 * if the call was to a noreturn function.  So get the ORC data for the

	 * call instruction itself.

	 */

	orc = orc_find(state->signal ? state->ip : state->ip - 1);

	if (!orc) {
@@ -662,6 +665,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, 
		state->sp = task->thread.sp;

		state->bp = READ_ONCE_NOCHECK(frame->bp);

		state->ip = READ_ONCE_NOCHECK(frame->ret_addr);

		state->signal = (void *)state->ip == ret_from_fork;

	}



	if (get_stack_info((unsigned long *)state->sp, state->task,

arch/x86/kernel/vmlinux.lds.S

+1 −0
Original line number Diff line number Diff line
@@ -358,6 +358,7 @@ SECTIONS 
	.bss : AT(ADDR(.bss) - LOAD_OFFSET) {

		__bss_start = .;

		*(.bss..page_aligned)

		. = ALIGN(PAGE_SIZE);

		*(BSS_MAIN)

		BSS_DECRYPTED

		. = ALIGN(PAGE_SIZE);

include/asm-generic/vmlinux.lds.h

+4 −1
Original line number Diff line number Diff line
@@ -341,7 +341,8 @@ 


#define PAGE_ALIGNED_DATA(page_align)					\

	. = ALIGN(page_align);						\

	*(.data..page_aligned)

	*(.data..page_aligned)						\

	. = ALIGN(page_align);



#define READ_MOSTLY_DATA(align)						\

	. = ALIGN(align);						\
@@ -737,7 +738,9 @@ 
	. = ALIGN(bss_align);						\

	.bss : AT(ADDR(.bss) - LOAD_OFFSET) {				\

		BSS_FIRST_SECTIONS					\

		. = ALIGN(PAGE_SIZE);					\

		*(.bss..page_aligned)					\

		. = ALIGN(PAGE_SIZE);					\

		*(.dynbss)						\

		*(BSS_MAIN)						\

		*(COMMON)						\

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