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Misc fixes:

Browse source 
- 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
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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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
This commit is contained in:
Linus Torvalds 2020-07-25 14:25:47 -07:00
commit fbe0d451bc
5 changed files with 28 additions and 18 deletions
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27
arch/x86/kernel/dumpstack.c
View file

@ -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> %"

5
arch/x86/kernel/stacktrace.c
View file

@ -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;
}

8
arch/x86/kernel/unwind_orc.c
View file

@ -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,

1
arch/x86/kernel/vmlinux.lds.S
View file

@ -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);

5
include/asm-generic/vmlinux.lds.h
View file

@ -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) \