[PATCH mm] kasan: print virtual mapping info in reports

[PATCH mm] kasan: print virtual mapping info in reports

[andrey.konovalov]

From: Andrey Konovalov <andreyknvl@google.com>

Print virtual mapping range and its creator in reports affecting virtual
mappings.

Also get physical page pointer for such mappings, so page information
gets printed as well.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

---

Note: no need to merge this patch into any of the KASAN vmalloc patches
that are already in mm, better to keep it separate.
---
 mm/kasan/report.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 137c2c0b09db..8002fb3c417d 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -260,8 +260,18 @@ static void print_address_description(void *addr, u8 tag)
 		pr_err(" %pS\n", addr);
 	}
 
+	if (is_vmalloc_addr(addr)) {
+		struct vm_struct *va = find_vm_area(addr);
+
+		pr_err("The buggy address belongs to the virtual mapping at\n"
+		       " [%px, %px) created by:\n"
+		       " %pS\n", va->addr, va->addr + va->size, va->caller);
+
+		page = vmalloc_to_page(page);
+	}
+
 	if (page) {
-		pr_err("The buggy address belongs to the page:\n");
+		pr_err("The buggy address belongs to the physical page:\n");
 		dump_page(page, "kasan: bad access detected");
 	}
 
-- 
2.25.1

Re: [PATCH mm] kasan: print virtual mapping info in reports

[Marco Elver]

On Wed, 16 Feb 2022 at 20:01, <andrey.konovalov@linux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@google.com>
>
> Print virtual mapping range and its creator in reports affecting virtual
> mappings.
>
> Also get physical page pointer for such mappings, so page information
> gets printed as well.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
>
> ---
>
> Note: no need to merge this patch into any of the KASAN vmalloc patches
> that are already in mm, better to keep it separate.
> ---
>  mm/kasan/report.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 137c2c0b09db..8002fb3c417d 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -260,8 +260,18 @@ static void print_address_description(void *addr, u8 tag)
>                 pr_err(" %pS\n", addr);
>         }
>
> +       if (is_vmalloc_addr(addr)) {
> +               struct vm_struct *va = find_vm_area(addr);
> +
> +               pr_err("The buggy address belongs to the virtual mapping at\n"
> +                      " [%px, %px) created by:\n"
> +                      " %pS\n", va->addr, va->addr + va->size, va->caller);

Can you show an example of what this looks like? It's not showing a
stack trace, so why not continue the line and just say "... created
by: %pS\n"

> +               page = vmalloc_to_page(page);
> +       }
> +
>         if (page) {
> -               pr_err("The buggy address belongs to the page:\n");
> +               pr_err("The buggy address belongs to the physical page:\n");
>                 dump_page(page, "kasan: bad access detected");
>         }
>
> --
> 2.25.1
>

Re: [PATCH mm] kasan: print virtual mapping info in reports

[Andrey Konovalov]

On Wed, Feb 16, 2022 at 8:31 PM Marco Elver <elver@google.com> wrote:
>
> On Wed, 16 Feb 2022 at 20:01, <andrey.konovalov@linux.dev> wrote:
> >
> > From: Andrey Konovalov <andreyknvl@google.com>
> >
> > Print virtual mapping range and its creator in reports affecting virtual
> > mappings.
> >
> > Also get physical page pointer for such mappings, so page information
> > gets printed as well.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> >
> > ---
> >
> > Note: no need to merge this patch into any of the KASAN vmalloc patches
> > that are already in mm, better to keep it separate.
> > ---
> >  mm/kasan/report.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> > index 137c2c0b09db..8002fb3c417d 100644
> > --- a/mm/kasan/report.c
> > +++ b/mm/kasan/report.c
> > @@ -260,8 +260,18 @@ static void print_address_description(void *addr, u8 tag)
> >                 pr_err(" %pS\n", addr);
> >         }
> >
> > +       if (is_vmalloc_addr(addr)) {
> > +               struct vm_struct *va = find_vm_area(addr);
> > +
> > +               pr_err("The buggy address belongs to the virtual mapping at\n"
> > +                      " [%px, %px) created by:\n"
> > +                      " %pS\n", va->addr, va->addr + va->size, va->caller);
>
> Can you show an example of what this looks like?

[   20.883723] The buggy address belongs to the virtual mapping at
[   20.883723]  [ffff8000081c9000, ffff8000081cb000) created by:
[   20.883723]  vmalloc_oob+0xd8/0x4dc

> It's not showing a stack trace,

No, only a single frame.

> so why not continue the line and just say "... created by: %pS\n"

Putting it on a separate line makes the line lengths looks more balanced.

Also, printing a frame on a separate line is consistent with the rest
of KASAN reporting code.

Re: [PATCH mm] kasan: print virtual mapping info in reports

[Marco Elver]

On Wed, 16 Feb 2022 at 21:42, Andrey Konovalov <andreyknvl@gmail.com> wrote:
>
> On Wed, Feb 16, 2022 at 8:31 PM Marco Elver <elver@google.com> wrote:
> >
> > On Wed, 16 Feb 2022 at 20:01, <andrey.konovalov@linux.dev> wrote:
> > >
> > > From: Andrey Konovalov <andreyknvl@google.com>
> > >
> > > Print virtual mapping range and its creator in reports affecting virtual
> > > mappings.
> > >
> > > Also get physical page pointer for such mappings, so page information
> > > gets printed as well.
> > >
> > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> > >
> > > ---
> > >
> > > Note: no need to merge this patch into any of the KASAN vmalloc patches
> > > that are already in mm, better to keep it separate.
> > > ---
> > >  mm/kasan/report.c | 12 +++++++++++-
> > >  1 file changed, 11 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> > > index 137c2c0b09db..8002fb3c417d 100644
> > > --- a/mm/kasan/report.c
> > > +++ b/mm/kasan/report.c
> > > @@ -260,8 +260,18 @@ static void print_address_description(void *addr, u8 tag)
> > >                 pr_err(" %pS\n", addr);
> > >         }
> > >
> > > +       if (is_vmalloc_addr(addr)) {
> > > +               struct vm_struct *va = find_vm_area(addr);
> > > +
> > > +               pr_err("The buggy address belongs to the virtual mapping at\n"
> > > +                      " [%px, %px) created by:\n"
> > > +                      " %pS\n", va->addr, va->addr + va->size, va->caller);
> >
> > Can you show an example of what this looks like?
>
> [   20.883723] The buggy address belongs to the virtual mapping at
> [   20.883723]  [ffff8000081c9000, ffff8000081cb000) created by:
> [   20.883723]  vmalloc_oob+0xd8/0x4dc
>
> > It's not showing a stack trace,
>
> No, only a single frame.
>
> > so why not continue the line and just say "... created by: %pS\n"
>
> Putting it on a separate line makes the line lengths looks more balanced.
>
> Also, printing a frame on a separate line is consistent with the rest
> of KASAN reporting code.

That's reasonable, thanks.

Reviewed-by: Marco Elver <elver@google.com>

Re: [PATCH mm] kasan: print virtual mapping info in reports

[Mark Rutland]

On Wed, Feb 16, 2022 at 08:01:37PM +0100, andrey.konovalov@linux.dev wrote:
> From: Andrey Konovalov <andreyknvl@google.com>
> 
> Print virtual mapping range and its creator in reports affecting virtual
> mappings.
> 
> Also get physical page pointer for such mappings, so page information
> gets printed as well.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> 
> ---
> 
> Note: no need to merge this patch into any of the KASAN vmalloc patches
> that are already in mm, better to keep it separate.
> ---
>  mm/kasan/report.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 137c2c0b09db..8002fb3c417d 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -260,8 +260,18 @@ static void print_address_description(void *addr, u8 tag)
>  		pr_err(" %pS\n", addr);
>  	}
>  
> +	if (is_vmalloc_addr(addr)) {
> +		struct vm_struct *va = find_vm_area(addr);
> +
> +		pr_err("The buggy address belongs to the virtual mapping at\n"
> +		       " [%px, %px) created by:\n"
> +		       " %pS\n", va->addr, va->addr + va->size, va->caller);

The return value of find_vm_area() needs a NULL check here;
is_vmalloc_addr(addr) just checks that `addr` is within the vmalloc VA
range, and doesn't guarantee that there is a vmap_area associated with
that `addr`.

Without the NULL-check, we'll blow up on the `va->addr` dereference and
will fail to make the report, which would be unfortunate.

Thanks,
Mark.

> +
> +		page = vmalloc_to_page(page);
> +	}
> +
>  	if (page) {
> -		pr_err("The buggy address belongs to the page:\n");
> +		pr_err("The buggy address belongs to the physical page:\n");
>  		dump_page(page, "kasan: bad access detected");
>  	}
>  
> -- 
> 2.25.1
> 

Re: [PATCH mm] kasan: print virtual mapping info in reports

[Andrey Konovalov]

On Thu, Feb 17, 2022 at 1:00 PM Mark Rutland <mark.rutland@arm.com> wrote:
>
> On Wed, Feb 16, 2022 at 08:01:37PM +0100, andrey.konovalov@linux.dev wrote:
> > From: Andrey Konovalov <andreyknvl@google.com>
> >
> > Print virtual mapping range and its creator in reports affecting virtual
> > mappings.
> >
> > Also get physical page pointer for such mappings, so page information
> > gets printed as well.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> >
> > ---
> >
> > Note: no need to merge this patch into any of the KASAN vmalloc patches
> > that are already in mm, better to keep it separate.
> > ---
> >  mm/kasan/report.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> > index 137c2c0b09db..8002fb3c417d 100644
> > --- a/mm/kasan/report.c
> > +++ b/mm/kasan/report.c
> > @@ -260,8 +260,18 @@ static void print_address_description(void *addr, u8 tag)
> >               pr_err(" %pS\n", addr);
> >       }
> >
> > +     if (is_vmalloc_addr(addr)) {
> > +             struct vm_struct *va = find_vm_area(addr);
> > +
> > +             pr_err("The buggy address belongs to the virtual mapping at\n"
> > +                    " [%px, %px) created by:\n"
> > +                    " %pS\n", va->addr, va->addr + va->size, va->caller);
>
> The return value of find_vm_area() needs a NULL check here;
> is_vmalloc_addr(addr) just checks that `addr` is within the vmalloc VA
> range, and doesn't guarantee that there is a vmap_area associated with
> that `addr`.
>
> Without the NULL-check, we'll blow up on the `va->addr` dereference and
> will fail to make the report, which would be unfortunate.

Indeed. Will fix in v2. Thanks, Mark!

[PATCH mm] kasan: print virtual mapping info in reports

[andrey.konovalov]

From: Andrey Konovalov <andreyknvl@google.com>

Print virtual mapping range and its creator in reports affecting virtual
mappings.

Also get physical page pointer for such mappings, so page information
gets printed as well.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

---

Note: no need to merge this patch into any of the KASAN vmalloc patches
that are already in mm, better to keep it separate.

Changes v1->v2:
- Add find_vm_area() return value NULL check as suggested by Mark Rutland.
---
 mm/kasan/report.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 137c2c0b09db..f64352008bb8 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -260,8 +260,21 @@ static void print_address_description(void *addr, u8 tag)
 		pr_err(" %pS\n", addr);
 	}
 
+	if (is_vmalloc_addr(addr)) {
+		struct vm_struct *va = find_vm_area(addr);
+
+		if (va) {
+			pr_err("The buggy address belongs to the virtual mapping at\n"
+			       " [%px, %px) created by:\n"
+			       " %pS\n",
+			       va->addr, va->addr + va->size, va->caller);
+
+			page = vmalloc_to_page(page);
+		}
+	}
+
 	if (page) {
-		pr_err("The buggy address belongs to the page:\n");
+		pr_err("The buggy address belongs to the physical page:\n");
 		dump_page(page, "kasan: bad access detected");
 	}
 
-- 
2.25.1