From d3eb8015ec4bd5d1afc01cabf9c0a72285173e21 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Fri, 31 Aug 2018 21:41:51 +0200 Subject: [PATCH] x86/process: Don't mix user/kernel regs in 64bit __show_regs() commit 9fe6299dde587788f245e9f7a5a1b296fad4e8c7 upstream. When the kernel.print-fatal-signals sysctl has been enabled, a simple userspace crash will cause the kernel to write a crash dump that contains, among other things, the kernel gsbase into dmesg. As suggested by Andy, limit output to pt_regs, FS_BASE and KERNEL_GS_BASE in this case. This also moves the bitness-specific logic from show_regs() into process_{32,64}.c. Fixes: 45807a1df9f5 ("vdso: print fatal signals") Signed-off-by: Jann Horn Signed-off-by: Thomas Gleixner Cc: "H. Peter Anvin" Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Greg Kroah-Hartman Link: https://lkml.kernel.org/r/20180831194151.123586-1-jannh@google.com [bwh: Backported to 3.16: - Keep using user_mode_vm() to in 32-bit show_regs() - Also update call to __show_regs() in kmemcheck - Don't add redundant rdmsrl()s in 64-bit __show_regs() - Adjust filenames, context] Signed-off-by: Ben Hutchings --- arch/x86/include/asm/kdebug.h | 12 +++++++++++- arch/x86/kernel/dumpstack_32.c | 2 +- arch/x86/kernel/dumpstack_64.c | 2 +- arch/x86/kernel/process_32.c | 4 ++-- arch/x86/kernel/process_64.c | 10 ++++++++-- arch/x86/mm/kmemcheck/error.c | 2 +- 6 files changed, 24 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h index 32ce71375b21..5683ea84a6fc 100644 --- a/arch/x86/include/asm/kdebug.h +++ b/arch/x86/include/asm/kdebug.h @@ -21,12 +21,22 @@ enum die_val { DIE_NMIUNKNOWN, }; +enum show_regs_mode { + SHOW_REGS_SHORT, + /* + * For when userspace crashed, but we don't think it's our fault, and + * therefore don't print kernel registers. + */ + SHOW_REGS_USER, + SHOW_REGS_ALL +}; + extern void printk_address(unsigned long address); extern void die(const char *, struct pt_regs *,long); extern int __must_check __die(const char *, struct pt_regs *, long); extern void show_trace(struct task_struct *t, struct pt_regs *regs, unsigned long *sp, unsigned long bp); -extern void __show_regs(struct pt_regs *regs, int all); +extern void __show_regs(struct pt_regs *regs, enum show_regs_mode); extern unsigned long oops_begin(void); extern void oops_end(unsigned long, struct pt_regs *, int signr); #ifdef CONFIG_KEXEC diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c index 5abd4cd4230c..cac129fa0e7f 100644 --- a/arch/x86/kernel/dumpstack_32.c +++ b/arch/x86/kernel/dumpstack_32.c @@ -123,7 +123,7 @@ void show_regs(struct pt_regs *regs) int i; show_regs_print_info(KERN_EMERG); - __show_regs(regs, !user_mode_vm(regs)); + __show_regs(regs, user_mode_vm(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL); /* * When in-kernel, we also print out the stack and code at the diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c index ff86f19b5758..879ab159aa49 100644 --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -301,7 +301,7 @@ void show_regs(struct pt_regs *regs) sp = regs->sp; show_regs_print_info(KERN_DEFAULT); - __show_regs(regs, 1); + __show_regs(regs, user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL); /* * When in-kernel, we also print out the stack and code at the diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 7bc86bbe7485..c72b7afd3e02 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -66,7 +66,7 @@ unsigned long thread_saved_pc(struct task_struct *tsk) return ((unsigned long *)tsk->thread.sp)[3]; } -void __show_regs(struct pt_regs *regs, int all) +void __show_regs(struct pt_regs *regs, enum show_regs_mode mode) { unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; unsigned long d0, d1, d2, d3, d6, d7; @@ -95,7 +95,7 @@ void __show_regs(struct pt_regs *regs, int all) printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n", (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); - if (!all) + if (mode != SHOW_REGS_ALL) return; cr0 = read_cr0(); diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 8eb41e06932c..512fb8c979ed 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -56,7 +56,7 @@ asmlinkage extern void ret_from_fork(void); __visible DEFINE_PER_CPU_USER_MAPPED(unsigned long, old_rsp); /* Prints also some state that isn't saved in the pt_regs */ -void __show_regs(struct pt_regs *regs, int all) +void __show_regs(struct pt_regs *regs, enum show_regs_mode mode) { unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L, fs, gs, shadowgs; unsigned long d0, d1, d2, d3, d6, d7; @@ -88,9 +88,15 @@ void __show_regs(struct pt_regs *regs, int all) rdmsrl(MSR_GS_BASE, gs); rdmsrl(MSR_KERNEL_GS_BASE, shadowgs); - if (!all) + if (mode == SHOW_REGS_SHORT) return; + if (mode == SHOW_REGS_USER) { + printk(KERN_DEFAULT "FS: %016lx GS: %016lx\n", + fs, shadowgs); + return; + } + cr0 = read_cr0(); cr2 = read_cr2(); cr3 = read_cr3(); diff --git a/arch/x86/mm/kmemcheck/error.c b/arch/x86/mm/kmemcheck/error.c index dab41876cdd5..efcdcef32e19 100644 --- a/arch/x86/mm/kmemcheck/error.c +++ b/arch/x86/mm/kmemcheck/error.c @@ -132,7 +132,7 @@ void kmemcheck_error_recall(void) break; } - __show_regs(&e->regs, 1); + __show_regs(&e->regs, SHOW_REGS_ALL); print_stack_trace(&e->trace, 0); }