* [PATCH] x86/process: don't mix user/kernel regs in 64bit __show_regs
@ 2018-08-31 19:41 Jann Horn
2018-08-31 20:11 ` Andy Lutomirski
2018-09-06 12:36 ` [tip:x86/urgent] x86/process: Don't mix user/kernel regs in 64bit __show_regs() tip-bot for Jann Horn
0 siblings, 2 replies; 5+ messages in thread
From: Jann Horn @ 2018-08-31 19:41 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, x86,
Andy Lutomirski, jannh
Cc: Borislav Petkov, Greg Kroah-Hartman, linux-kernel
When the kernel.print-fatal-signals sysctl has been enabled (I don't know
whether anyone actually enables it), 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.
Signed-off-by: Jann Horn <jannh@google.com>
Fixes: 45807a1df9f5 ("vdso: print fatal signals")
---
@Andy: Does this look like what you had in mind?
Does this need a CC stable tag? I haven't put one on it for now.
arch/x86/include/asm/kdebug.h | 12 +++++++++++-
arch/x86/kernel/dumpstack.c | 11 +++--------
arch/x86/kernel/process_32.c | 4 ++--
arch/x86/kernel/process_64.c | 12 ++++++++++--
4 files changed, 26 insertions(+), 13 deletions(-)
diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h
index 395c9631e000..75f1e35e7c15 100644
--- a/arch/x86/include/asm/kdebug.h
+++ b/arch/x86/include/asm/kdebug.h
@@ -22,10 +22,20 @@ 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 die(const char *, struct pt_regs *,long);
extern int __must_check __die(const char *, struct pt_regs *, long);
extern void show_stack_regs(struct pt_regs *regs);
-extern void __show_regs(struct pt_regs *regs, int all);
+extern void __show_regs(struct pt_regs *regs, enum show_regs_mode);
extern void show_iret_regs(struct pt_regs *regs);
extern unsigned long oops_begin(void);
extern void oops_end(unsigned long, struct pt_regs *, int signr);
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 9c8652974f8e..574fe5d97ba2 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -135,7 +135,7 @@ static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
* they can be printed in the right context.
*/
if (!partial && on_stack(info, regs, sizeof(*regs))) {
- __show_regs(regs, 0);
+ __show_regs(regs, SHOW_REGS_SHORT);
} else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
IRET_FRAME_SIZE)) {
@@ -333,7 +333,7 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
oops_exit();
/* Executive summary in case the oops scrolled away */
- __show_regs(&exec_summary_regs, true);
+ __show_regs(&exec_summary_regs, SHOW_REGS_ALL);
if (!signr)
return;
@@ -393,14 +393,9 @@ void die(const char *str, struct pt_regs *regs, long err)
void show_regs(struct pt_regs *regs)
{
- bool all = true;
-
show_regs_print_info(KERN_DEFAULT);
- if (IS_ENABLED(CONFIG_X86_32))
- all = !user_mode(regs);
-
- __show_regs(regs, all);
+ __show_regs(regs, user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL);
/*
* When in-kernel, we also print out the stack at the time of the fault..
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 2924fd447e61..5046a3c9dec2 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -59,7 +59,7 @@
#include <asm/intel_rdt_sched.h>
#include <asm/proto.h>
-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;
@@ -85,7 +85,7 @@ void __show_regs(struct pt_regs *regs, int all)
printk(KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n",
(u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss, regs->flags);
- 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 a451bc374b9b..ea5ea850348d 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -62,7 +62,7 @@
__visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
/* 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;
@@ -87,9 +87,17 @@ void __show_regs(struct pt_regs *regs, int all)
printk(KERN_DEFAULT "R13: %016lx R14: %016lx R15: %016lx\n",
regs->r13, regs->r14, regs->r15);
- if (!all)
+ if (mode == SHOW_REGS_SHORT)
return;
+ if (mode == SHOW_REGS_USER) {
+ rdmsrl(MSR_FS_BASE, fs);
+ rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);
+ printk(KERN_DEFAULT "FS: %016lx GS: %016lx\n",
+ fs, shadowgs);
+ return;
+ }
+
asm("movl %%ds,%0" : "=r" (ds));
asm("movl %%cs,%0" : "=r" (cs));
asm("movl %%es,%0" : "=r" (es));
--
2.19.0.rc1.350.ge57e33dbd1-goog
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/process: don't mix user/kernel regs in 64bit __show_regs
2018-08-31 19:41 [PATCH] x86/process: don't mix user/kernel regs in 64bit __show_regs Jann Horn
@ 2018-08-31 20:11 ` Andy Lutomirski
2018-09-06 11:10 ` Jann Horn
2018-09-06 12:36 ` [tip:x86/urgent] x86/process: Don't mix user/kernel regs in 64bit __show_regs() tip-bot for Jann Horn
1 sibling, 1 reply; 5+ messages in thread
From: Andy Lutomirski @ 2018-08-31 20:11 UTC (permalink / raw)
To: Jann Horn
Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, X86 ML,
Andy Lutomirski, Borislav Petkov, Greg Kroah-Hartman, LKML
On Fri, Aug 31, 2018 at 12:41 PM, Jann Horn <jannh@google.com> wrote:
> When the kernel.print-fatal-signals sysctl has been enabled (I don't know
> whether anyone actually enables it), 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.
>
> Signed-off-by: Jann Horn <jannh@google.com>
> Fixes: 45807a1df9f5 ("vdso: print fatal signals")
> ---
> @Andy: Does this look like what you had in mind?
Yes.
Although there's another option: remove print-fatal-signals.
>
> Does this need a CC stable tag? I haven't put one on it for now.
Probably.
>
> arch/x86/include/asm/kdebug.h | 12 +++++++++++-
> arch/x86/kernel/dumpstack.c | 11 +++--------
> arch/x86/kernel/process_32.c | 4 ++--
> arch/x86/kernel/process_64.c | 12 ++++++++++--
> 4 files changed, 26 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h
> index 395c9631e000..75f1e35e7c15 100644
> --- a/arch/x86/include/asm/kdebug.h
> +++ b/arch/x86/include/asm/kdebug.h
> @@ -22,10 +22,20 @@ 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 die(const char *, struct pt_regs *,long);
> extern int __must_check __die(const char *, struct pt_regs *, long);
> extern void show_stack_regs(struct pt_regs *regs);
> -extern void __show_regs(struct pt_regs *regs, int all);
> +extern void __show_regs(struct pt_regs *regs, enum show_regs_mode);
> extern void show_iret_regs(struct pt_regs *regs);
> extern unsigned long oops_begin(void);
> extern void oops_end(unsigned long, struct pt_regs *, int signr);
> diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> index 9c8652974f8e..574fe5d97ba2 100644
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -135,7 +135,7 @@ static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
> * they can be printed in the right context.
> */
> if (!partial && on_stack(info, regs, sizeof(*regs))) {
> - __show_regs(regs, 0);
> + __show_regs(regs, SHOW_REGS_SHORT);
>
> } else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
> IRET_FRAME_SIZE)) {
> @@ -333,7 +333,7 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
> oops_exit();
>
> /* Executive summary in case the oops scrolled away */
> - __show_regs(&exec_summary_regs, true);
> + __show_regs(&exec_summary_regs, SHOW_REGS_ALL);
>
> if (!signr)
> return;
> @@ -393,14 +393,9 @@ void die(const char *str, struct pt_regs *regs, long err)
>
> void show_regs(struct pt_regs *regs)
> {
> - bool all = true;
> -
> show_regs_print_info(KERN_DEFAULT);
>
> - if (IS_ENABLED(CONFIG_X86_32))
> - all = !user_mode(regs);
> -
> - __show_regs(regs, all);
> + __show_regs(regs, user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL);
>
> /*
> * When in-kernel, we also print out the stack at the time of the fault..
> diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
> index 2924fd447e61..5046a3c9dec2 100644
> --- a/arch/x86/kernel/process_32.c
> +++ b/arch/x86/kernel/process_32.c
> @@ -59,7 +59,7 @@
> #include <asm/intel_rdt_sched.h>
> #include <asm/proto.h>
>
> -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;
> @@ -85,7 +85,7 @@ void __show_regs(struct pt_regs *regs, int all)
> printk(KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n",
> (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss, regs->flags);
>
> - 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 a451bc374b9b..ea5ea850348d 100644
> --- a/arch/x86/kernel/process_64.c
> +++ b/arch/x86/kernel/process_64.c
> @@ -62,7 +62,7 @@
> __visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
>
> /* 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;
> @@ -87,9 +87,17 @@ void __show_regs(struct pt_regs *regs, int all)
> printk(KERN_DEFAULT "R13: %016lx R14: %016lx R15: %016lx\n",
> regs->r13, regs->r14, regs->r15);
>
> - if (!all)
> + if (mode == SHOW_REGS_SHORT)
> return;
>
> + if (mode == SHOW_REGS_USER) {
> + rdmsrl(MSR_FS_BASE, fs);
> + rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);
> + printk(KERN_DEFAULT "FS: %016lx GS: %016lx\n",
> + fs, shadowgs);
> + return;
> + }
> +
> asm("movl %%ds,%0" : "=r" (ds));
> asm("movl %%cs,%0" : "=r" (cs));
> asm("movl %%es,%0" : "=r" (es));
> --
> 2.19.0.rc1.350.ge57e33dbd1-goog
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/process: don't mix user/kernel regs in 64bit __show_regs
2018-08-31 20:11 ` Andy Lutomirski
@ 2018-09-06 11:10 ` Jann Horn
2018-09-06 12:31 ` Thomas Gleixner
0 siblings, 1 reply; 5+ messages in thread
From: Jann Horn @ 2018-09-06 11:10 UTC (permalink / raw)
To: Andy Lutomirski, Ingo Molnar
Cc: Thomas Gleixner, H . Peter Anvin, the arch/x86 maintainers,
bpetkov, Greg Kroah-Hartman, kernel list
On Fri, Aug 31, 2018 at 10:12 PM Andy Lutomirski <luto@kernel.org> wrote:
>
> On Fri, Aug 31, 2018 at 12:41 PM, Jann Horn <jannh@google.com> wrote:
> > When the kernel.print-fatal-signals sysctl has been enabled (I don't know
> > whether anyone actually enables it), 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.
> >
> > Signed-off-by: Jann Horn <jannh@google.com>
> > Fixes: 45807a1df9f5 ("vdso: print fatal signals")
> > ---
> > @Andy: Does this look like what you had in mind?
>
> Yes.
>
> Although there's another option: remove print-fatal-signals.
Who wants to decide? Ingo, it's your feature - what do you think?
> > Does this need a CC stable tag? I haven't put one on it for now.
>
> Probably.
>
> >
> > arch/x86/include/asm/kdebug.h | 12 +++++++++++-
> > arch/x86/kernel/dumpstack.c | 11 +++--------
> > arch/x86/kernel/process_32.c | 4 ++--
> > arch/x86/kernel/process_64.c | 12 ++++++++++--
> > 4 files changed, 26 insertions(+), 13 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h
> > index 395c9631e000..75f1e35e7c15 100644
> > --- a/arch/x86/include/asm/kdebug.h
> > +++ b/arch/x86/include/asm/kdebug.h
> > @@ -22,10 +22,20 @@ 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 die(const char *, struct pt_regs *,long);
> > extern int __must_check __die(const char *, struct pt_regs *, long);
> > extern void show_stack_regs(struct pt_regs *regs);
> > -extern void __show_regs(struct pt_regs *regs, int all);
> > +extern void __show_regs(struct pt_regs *regs, enum show_regs_mode);
> > extern void show_iret_regs(struct pt_regs *regs);
> > extern unsigned long oops_begin(void);
> > extern void oops_end(unsigned long, struct pt_regs *, int signr);
> > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> > index 9c8652974f8e..574fe5d97ba2 100644
> > --- a/arch/x86/kernel/dumpstack.c
> > +++ b/arch/x86/kernel/dumpstack.c
> > @@ -135,7 +135,7 @@ static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
> > * they can be printed in the right context.
> > */
> > if (!partial && on_stack(info, regs, sizeof(*regs))) {
> > - __show_regs(regs, 0);
> > + __show_regs(regs, SHOW_REGS_SHORT);
> >
> > } else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
> > IRET_FRAME_SIZE)) {
> > @@ -333,7 +333,7 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
> > oops_exit();
> >
> > /* Executive summary in case the oops scrolled away */
> > - __show_regs(&exec_summary_regs, true);
> > + __show_regs(&exec_summary_regs, SHOW_REGS_ALL);
> >
> > if (!signr)
> > return;
> > @@ -393,14 +393,9 @@ void die(const char *str, struct pt_regs *regs, long err)
> >
> > void show_regs(struct pt_regs *regs)
> > {
> > - bool all = true;
> > -
> > show_regs_print_info(KERN_DEFAULT);
> >
> > - if (IS_ENABLED(CONFIG_X86_32))
> > - all = !user_mode(regs);
> > -
> > - __show_regs(regs, all);
> > + __show_regs(regs, user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL);
> >
> > /*
> > * When in-kernel, we also print out the stack at the time of the fault..
> > diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
> > index 2924fd447e61..5046a3c9dec2 100644
> > --- a/arch/x86/kernel/process_32.c
> > +++ b/arch/x86/kernel/process_32.c
> > @@ -59,7 +59,7 @@
> > #include <asm/intel_rdt_sched.h>
> > #include <asm/proto.h>
> >
> > -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;
> > @@ -85,7 +85,7 @@ void __show_regs(struct pt_regs *regs, int all)
> > printk(KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n",
> > (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss, regs->flags);
> >
> > - 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 a451bc374b9b..ea5ea850348d 100644
> > --- a/arch/x86/kernel/process_64.c
> > +++ b/arch/x86/kernel/process_64.c
> > @@ -62,7 +62,7 @@
> > __visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
> >
> > /* 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;
> > @@ -87,9 +87,17 @@ void __show_regs(struct pt_regs *regs, int all)
> > printk(KERN_DEFAULT "R13: %016lx R14: %016lx R15: %016lx\n",
> > regs->r13, regs->r14, regs->r15);
> >
> > - if (!all)
> > + if (mode == SHOW_REGS_SHORT)
> > return;
> >
> > + if (mode == SHOW_REGS_USER) {
> > + rdmsrl(MSR_FS_BASE, fs);
> > + rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);
> > + printk(KERN_DEFAULT "FS: %016lx GS: %016lx\n",
> > + fs, shadowgs);
> > + return;
> > + }
> > +
> > asm("movl %%ds,%0" : "=r" (ds));
> > asm("movl %%cs,%0" : "=r" (cs));
> > asm("movl %%es,%0" : "=r" (es));
> > --
> > 2.19.0.rc1.350.ge57e33dbd1-goog
> >
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/process: don't mix user/kernel regs in 64bit __show_regs
2018-09-06 11:10 ` Jann Horn
@ 2018-09-06 12:31 ` Thomas Gleixner
0 siblings, 0 replies; 5+ messages in thread
From: Thomas Gleixner @ 2018-09-06 12:31 UTC (permalink / raw)
To: Jann Horn
Cc: Andy Lutomirski, Ingo Molnar, H . Peter Anvin,
the arch/x86 maintainers, bpetkov, Greg Kroah-Hartman,
kernel list
On Thu, 6 Sep 2018, Jann Horn wrote:
> On Fri, Aug 31, 2018 at 10:12 PM Andy Lutomirski <luto@kernel.org> wrote:
> >
> > On Fri, Aug 31, 2018 at 12:41 PM, Jann Horn <jannh@google.com> wrote:
> > > When the kernel.print-fatal-signals sysctl has been enabled (I don't know
> > > whether anyone actually enables it), 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.
> > >
> > > Signed-off-by: Jann Horn <jannh@google.com>
> > > Fixes: 45807a1df9f5 ("vdso: print fatal signals")
> > > ---
> > > @Andy: Does this look like what you had in mind?
> >
> > Yes.
> >
> > Although there's another option: remove print-fatal-signals.
>
> Who wants to decide? Ingo, it's your feature - what do you think?
It seems to be documented for trouble shooting in lots of places and the
fix is not horrible. So lets keep it.
Thanks,
tglx
^ permalink raw reply [flat|nested] 5+ messages in thread
* [tip:x86/urgent] x86/process: Don't mix user/kernel regs in 64bit __show_regs()
2018-08-31 19:41 [PATCH] x86/process: don't mix user/kernel regs in 64bit __show_regs Jann Horn
2018-08-31 20:11 ` Andy Lutomirski
@ 2018-09-06 12:36 ` tip-bot for Jann Horn
1 sibling, 0 replies; 5+ messages in thread
From: tip-bot for Jann Horn @ 2018-09-06 12:36 UTC (permalink / raw)
To: linux-tip-commits
Cc: jannh, hpa, mingo, tglx, bpetkov, luto, linux-kernel, gregkh
Commit-ID: 9fe6299dde587788f245e9f7a5a1b296fad4e8c7
Gitweb: https://git.kernel.org/tip/9fe6299dde587788f245e9f7a5a1b296fad4e8c7
Author: Jann Horn <jannh@google.com>
AuthorDate: Fri, 31 Aug 2018 21:41:51 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 6 Sep 2018 14:33:12 +0200
x86/process: Don't mix user/kernel regs in 64bit __show_regs()
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 <jannh@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180831194151.123586-1-jannh@google.com
---
arch/x86/include/asm/kdebug.h | 12 +++++++++++-
arch/x86/kernel/dumpstack.c | 11 +++--------
arch/x86/kernel/process_32.c | 4 ++--
arch/x86/kernel/process_64.c | 12 ++++++++++--
4 files changed, 26 insertions(+), 13 deletions(-)
diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h
index 395c9631e000..75f1e35e7c15 100644
--- a/arch/x86/include/asm/kdebug.h
+++ b/arch/x86/include/asm/kdebug.h
@@ -22,10 +22,20 @@ 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 die(const char *, struct pt_regs *,long);
extern int __must_check __die(const char *, struct pt_regs *, long);
extern void show_stack_regs(struct pt_regs *regs);
-extern void __show_regs(struct pt_regs *regs, int all);
+extern void __show_regs(struct pt_regs *regs, enum show_regs_mode);
extern void show_iret_regs(struct pt_regs *regs);
extern unsigned long oops_begin(void);
extern void oops_end(unsigned long, struct pt_regs *, int signr);
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index f56895106ccf..2b5886401e5f 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -146,7 +146,7 @@ static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
* they can be printed in the right context.
*/
if (!partial && on_stack(info, regs, sizeof(*regs))) {
- __show_regs(regs, 0);
+ __show_regs(regs, SHOW_REGS_SHORT);
} else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
IRET_FRAME_SIZE)) {
@@ -344,7 +344,7 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
oops_exit();
/* Executive summary in case the oops scrolled away */
- __show_regs(&exec_summary_regs, true);
+ __show_regs(&exec_summary_regs, SHOW_REGS_ALL);
if (!signr)
return;
@@ -407,14 +407,9 @@ void die(const char *str, struct pt_regs *regs, long err)
void show_regs(struct pt_regs *regs)
{
- bool all = true;
-
show_regs_print_info(KERN_DEFAULT);
- if (IS_ENABLED(CONFIG_X86_32))
- all = !user_mode(regs);
-
- __show_regs(regs, all);
+ __show_regs(regs, user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL);
/*
* When in-kernel, we also print out the stack at the time of the fault..
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 2924fd447e61..5046a3c9dec2 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -59,7 +59,7 @@
#include <asm/intel_rdt_sched.h>
#include <asm/proto.h>
-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;
@@ -85,7 +85,7 @@ void __show_regs(struct pt_regs *regs, int all)
printk(KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n",
(u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss, regs->flags);
- 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 a451bc374b9b..ea5ea850348d 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -62,7 +62,7 @@
__visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
/* 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;
@@ -87,9 +87,17 @@ void __show_regs(struct pt_regs *regs, int all)
printk(KERN_DEFAULT "R13: %016lx R14: %016lx R15: %016lx\n",
regs->r13, regs->r14, regs->r15);
- if (!all)
+ if (mode == SHOW_REGS_SHORT)
return;
+ if (mode == SHOW_REGS_USER) {
+ rdmsrl(MSR_FS_BASE, fs);
+ rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);
+ printk(KERN_DEFAULT "FS: %016lx GS: %016lx\n",
+ fs, shadowgs);
+ return;
+ }
+
asm("movl %%ds,%0" : "=r" (ds));
asm("movl %%cs,%0" : "=r" (cs));
asm("movl %%es,%0" : "=r" (es));
^ permalink raw reply related [flat|nested] 5+ messages in thread
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-- links below jump to the message on this page --
2018-08-31 19:41 [PATCH] x86/process: don't mix user/kernel regs in 64bit __show_regs Jann Horn
2018-08-31 20:11 ` Andy Lutomirski
2018-09-06 11:10 ` Jann Horn
2018-09-06 12:31 ` Thomas Gleixner
2018-09-06 12:36 ` [tip:x86/urgent] x86/process: Don't mix user/kernel regs in 64bit __show_regs() tip-bot for Jann Horn
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