* [PATCH v2] powerpc/mm: make NULL pointer deferences explicit on bad page faults.
@ 2018-12-14 15:23 ` Christophe Leroy
0 siblings, 0 replies; 5+ messages in thread
From: Christophe Leroy @ 2018-12-14 15:23 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
Cc: linux-kernel, linuxppc-dev
As several other arches including x86, this patch makes it explicit
that a bad page fault is a NULL pointer dereference when the fault
address is lower than PAGE_SIZE
In the mean time, this page makes all bad_page_fault() messages shorter
so that they remain on one single line. And it prefixes them by "BUG: "
so that they get easily greped.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
v2: Taking into account comments from Michael
arch/powerpc/mm/fault.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 01b9bcc7fa85..3398291f4785 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -636,21 +636,24 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
switch (TRAP(regs)) {
case 0x300:
case 0x380:
- printk(KERN_ALERT "Unable to handle kernel paging request for "
- "data at address 0x%08lx\n", regs->dar);
+ if (regs->dar < PAGE_SIZE)
+ pr_alert("BUG: Kernel NULL pointer dereference");
+ else
+ pr_alert("BUG: Unable to handle kernel data access");
+ pr_cont(" at 0x%08lx\n", regs->dar);
break;
case 0x400:
case 0x480:
- printk(KERN_ALERT "Unable to handle kernel paging request for "
- "instruction fetch\n");
+ pr_alert("BUG: Unable to handle kernel instruction fetch%s",
+ regs->nip < PAGE_SIZE ? " (NULL pointer ?)\n" : "\n");
break;
case 0x600:
- printk(KERN_ALERT "Unable to handle kernel paging request for "
- "unaligned access at address 0x%08lx\n", regs->dar);
+ pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
+ regs->dar);
break;
default:
- printk(KERN_ALERT "Unable to handle kernel paging request for "
- "unknown fault\n");
+ pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
+ regs->dar);
break;
}
printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
--
2.13.3
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH v2] powerpc/mm: make NULL pointer deferences explicit on bad page faults.
@ 2018-12-14 15:23 ` Christophe Leroy
0 siblings, 0 replies; 5+ messages in thread
From: Christophe Leroy @ 2018-12-14 15:23 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
Cc: linuxppc-dev, linux-kernel
As several other arches including x86, this patch makes it explicit
that a bad page fault is a NULL pointer dereference when the fault
address is lower than PAGE_SIZE
In the mean time, this page makes all bad_page_fault() messages shorter
so that they remain on one single line. And it prefixes them by "BUG: "
so that they get easily greped.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
v2: Taking into account comments from Michael
arch/powerpc/mm/fault.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 01b9bcc7fa85..3398291f4785 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -636,21 +636,24 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
switch (TRAP(regs)) {
case 0x300:
case 0x380:
- printk(KERN_ALERT "Unable to handle kernel paging request for "
- "data at address 0x%08lx\n", regs->dar);
+ if (regs->dar < PAGE_SIZE)
+ pr_alert("BUG: Kernel NULL pointer dereference");
+ else
+ pr_alert("BUG: Unable to handle kernel data access");
+ pr_cont(" at 0x%08lx\n", regs->dar);
break;
case 0x400:
case 0x480:
- printk(KERN_ALERT "Unable to handle kernel paging request for "
- "instruction fetch\n");
+ pr_alert("BUG: Unable to handle kernel instruction fetch%s",
+ regs->nip < PAGE_SIZE ? " (NULL pointer ?)\n" : "\n");
break;
case 0x600:
- printk(KERN_ALERT "Unable to handle kernel paging request for "
- "unaligned access at address 0x%08lx\n", regs->dar);
+ pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
+ regs->dar);
break;
default:
- printk(KERN_ALERT "Unable to handle kernel paging request for "
- "unknown fault\n");
+ pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
+ regs->dar);
break;
}
printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
--
2.13.3
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH v2] powerpc/mm: make NULL pointer deferences explicit on bad page faults.
2018-12-14 15:23 ` Christophe Leroy
@ 2018-12-17 12:28 ` Michael Ellerman
-1 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2018-12-17 12:28 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras
Cc: linux-kernel, linuxppc-dev
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 01b9bcc7fa85..3398291f4785 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -636,21 +636,24 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
> switch (TRAP(regs)) {
> case 0x300:
> case 0x380:
> - printk(KERN_ALERT "Unable to handle kernel paging request for "
> - "data at address 0x%08lx\n", regs->dar);
> + if (regs->dar < PAGE_SIZE)
> + pr_alert("BUG: Kernel NULL pointer dereference");
> + else
> + pr_alert("BUG: Unable to handle kernel data access");
> + pr_cont(" at 0x%08lx\n", regs->dar);
It's best to avoid pr_cont() as it can lead to interleaving, so I
rewrote this as:
pr_alert("BUG: %s at 0x%08lx\n",
regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
"Unable to handle kernel data access", regs->dar);
> break;
> case 0x400:
> case 0x480:
> - printk(KERN_ALERT "Unable to handle kernel paging request for "
> - "instruction fetch\n");
> + pr_alert("BUG: Unable to handle kernel instruction fetch%s",
> + regs->nip < PAGE_SIZE ? " (NULL pointer ?)\n" : "\n");
I dropped the space here ^
cheers
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v2] powerpc/mm: make NULL pointer deferences explicit on bad page faults.
@ 2018-12-17 12:28 ` Michael Ellerman
0 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2018-12-17 12:28 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras
Cc: linuxppc-dev, linux-kernel
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 01b9bcc7fa85..3398291f4785 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -636,21 +636,24 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
> switch (TRAP(regs)) {
> case 0x300:
> case 0x380:
> - printk(KERN_ALERT "Unable to handle kernel paging request for "
> - "data at address 0x%08lx\n", regs->dar);
> + if (regs->dar < PAGE_SIZE)
> + pr_alert("BUG: Kernel NULL pointer dereference");
> + else
> + pr_alert("BUG: Unable to handle kernel data access");
> + pr_cont(" at 0x%08lx\n", regs->dar);
It's best to avoid pr_cont() as it can lead to interleaving, so I
rewrote this as:
pr_alert("BUG: %s at 0x%08lx\n",
regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
"Unable to handle kernel data access", regs->dar);
> break;
> case 0x400:
> case 0x480:
> - printk(KERN_ALERT "Unable to handle kernel paging request for "
> - "instruction fetch\n");
> + pr_alert("BUG: Unable to handle kernel instruction fetch%s",
> + regs->nip < PAGE_SIZE ? " (NULL pointer ?)\n" : "\n");
I dropped the space here ^
cheers
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [v2] powerpc/mm: make NULL pointer deferences explicit on bad page faults.
2018-12-14 15:23 ` Christophe Leroy
(?)
(?)
@ 2018-12-22 9:54 ` Michael Ellerman
-1 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2018-12-22 9:54 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras
Cc: linuxppc-dev, linux-kernel
On Fri, 2018-12-14 at 15:23:33 UTC, Christophe Leroy wrote:
> As several other arches including x86, this patch makes it explicit
> that a bad page fault is a NULL pointer dereference when the fault
> address is lower than PAGE_SIZE
>
> In the mean time, this page makes all bad_page_fault() messages shorter
> so that they remain on one single line. And it prefixes them by "BUG: "
> so that they get easily greped.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/49a502ea23bf9dec47f8f3c3960909
cheers
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2018-12-22 17:02 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2018-12-14 15:23 [PATCH v2] powerpc/mm: make NULL pointer deferences explicit on bad page faults Christophe Leroy
2018-12-14 15:23 ` Christophe Leroy
2018-12-17 12:28 ` Michael Ellerman
2018-12-17 12:28 ` Michael Ellerman
2018-12-22 9:54 ` [v2] " Michael Ellerman
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