Messages in this thread Patch in this message | | | From | Tycho Andersen <> | Subject | [PATCH v2] x86/entry: re-enable interrupts before exiting | Date | Fri, 5 Apr 2019 10:19:29 -0600 |
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If the kernel oopses in an interrupt, nothing re-enables interrupts:
Aug 23 19:30:27 xpfo kernel: [ 38.302714] BUG: sleeping function called from invalid context at ./include/linux/percpu-rwsem.h:33 Aug 23 19:30:27 xpfo kernel: [ 38.303837] in_atomic(): 0, irqs_disabled(): 1, pid: 1970, name: lkdtm_xpfo_test Aug 23 19:30:27 xpfo kernel: [ 38.304758] CPU: 3 PID: 1970 Comm: lkdtm_xpfo_test Tainted: G D 4.13.0-rc5+ #228 Aug 23 19:30:27 xpfo kernel: [ 38.305813] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.1-1ubuntu1 04/01/2014 Aug 23 19:30:27 xpfo kernel: [ 38.306926] Call Trace: Aug 23 19:30:27 xpfo kernel: [ 38.307243] dump_stack+0x63/0x8b Aug 23 19:30:27 xpfo kernel: [ 38.307665] ___might_sleep+0xec/0x110 Aug 23 19:30:27 xpfo kernel: [ 38.308139] __might_sleep+0x45/0x80 Aug 23 19:30:27 xpfo kernel: [ 38.308593] exit_signals+0x21/0x1c0 Aug 23 19:30:27 xpfo kernel: [ 38.309046] ? blocking_notifier_call_chain+0x11/0x20 Aug 23 19:30:27 xpfo kernel: [ 38.309677] do_exit+0x98/0xbf0 Aug 23 19:30:27 xpfo kernel: [ 38.310078] ? smp_reader+0x27/0x40 [lkdtm] Aug 23 19:30:27 xpfo kernel: [ 38.310604] ? kthread+0x10f/0x150 Aug 23 19:30:27 xpfo kernel: [ 38.311045] ? read_user_with_flags+0x60/0x60 [lkdtm] Aug 23 19:30:27 xpfo kernel: [ 38.311680] rewind_stack_do_exit+0x17/0x20
do_exit() expects to be called in a well-defined environment, so let's re-enable interrupts after unwinding the stack, in case they were disabled.
Note that if any spinlocks are held, etc. we'll also get the above warning, so this isn't a silver bullet. So, let's add a C helper in case someone wants to add fancier lock busting or if we've forgotten to unwind something else.
Signed-off-by: Tycho Andersen <tycho@tycho.ws> CC: Josh Poimboeuf <jpoimboe@redhat.com> --- I split this out from the XPFO series since it's mostly unrelated, and is just a bug I found while working on that series.
v2: whitelist __finish_rewind_stack_do_exit() as a noreturn function in objtool (Josh) --- arch/x86/entry/common.c | 10 ++++++++++ arch/x86/entry/entry_32.S | 2 +- arch/x86/entry/entry_64.S | 2 +- tools/objtool/check.c | 1 + 4 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 7bc105f47d21..4e9c54e0495f 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -427,3 +427,13 @@ __visible long do_fast_syscall_32(struct pt_regs *regs) #endif } #endif + +void __noreturn __finish_rewind_stack_do_exit(long code) +{ + /* + * If we oopsed in an interrupt handler, interrupts may be off. Let's turn + * them back on before going back to "normal" code. + */ + local_irq_enable(); + do_exit(code); +} diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index d309f30cf7af..095b8770e3b0 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -1507,6 +1507,6 @@ ENTRY(rewind_stack_do_exit) movl PER_CPU_VAR(cpu_current_top_of_stack), %esi leal -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%esi), %esp - call do_exit + call __finish_rewind_stack_do_exit 1: jmp 1b END(rewind_stack_do_exit) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 1f0efdb7b629..890a66d17f31 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1672,5 +1672,5 @@ ENTRY(rewind_stack_do_exit) leaq -PTREGS_SIZE(%rax), %rsp UNWIND_HINT_FUNC sp_offset=PTREGS_SIZE - call do_exit + call __finish_rewind_stack_do_exit END(rewind_stack_do_exit) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 5dde107083c6..f88f8f0b3f6e 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -156,6 +156,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func, "__stack_chk_fail", "panic", "do_exit", + "__finish_rewind_stack_do_exit", "do_task_dead", "__module_put_and_exit", "complete_and_exit", -- 2.19.1
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