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x86/process: Don't mix user/kernel regs in 64bit __show_regs()

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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: 45807a1df9 ("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
This commit is contained in:
Jann Horn 2018-08-31 21:41:51 +02:00 committed by Thomas Gleixner
parent 17f6bac224
commit 9fe6299dde
4 changed files with 26 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
arch/x86/include/asm/kdebug.h
View File

@ -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);

11
arch/x86/kernel/dumpstack.c
View File

@ -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..

4
arch/x86/kernel/process_32.c
View File

@ -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();

12
arch/x86/kernel/process_64.c
View File

@ -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));