* Re: [PATCH] mm/slub: Add taint after the errors are printed
2021-06-16 16:25 [PATCH] mm/slub: Add taint after the errors are printed Georgi Djakov
@ 2021-06-16 16:34 ` Vlastimil Babka
2021-06-16 22:13 ` Rafael Aquini
2021-06-16 22:11 ` Rafael Aquini
` (3 subsequent siblings)
4 siblings, 1 reply; 8+ messages in thread
From: Vlastimil Babka @ 2021-06-16 16:34 UTC (permalink / raw)
To: Georgi Djakov, akpm, iamjoonsoo.kim, rientjes, penberg, cl
Cc: linux-mm, linux-kernel, djakov
On 6/16/21 6:25 PM, Georgi Djakov wrote:
> When running the kernel with panic_on_taint, the usual slub debug error
> messages are not being printed when object corruption happens. That's
> because we panic in add_taint(), which is called before printing the
> additional information. This is a bit unfortunate as the error messages
> are actually very useful, especially before a panic. Let's fix this by
> moving add_taint() after the errors are printed on the console.
>
> Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
Makes sense.
While at it, I wonder if we should use LOCKDEP_STILL_OK instead of
LOCKDEP_NOW_UNRELIABLE. Isn't it too pessimistic to assume that some slab's
memory corruption hit some lock state?
> ---
> mm/slub.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index a8b0daa1a307..ce7b8e4551b5 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -719,8 +719,6 @@ static void slab_bug(struct kmem_cache *s, char *fmt, ...)
> pr_err("=============================================================================\n");
> pr_err("BUG %s (%s): %pV\n", s->name, print_tainted(), &vaf);
> pr_err("-----------------------------------------------------------------------------\n\n");
> -
> - add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> va_end(args);
> }
>
> @@ -801,6 +799,7 @@ void object_err(struct kmem_cache *s, struct page *page,
>
> slab_bug(s, "%s", reason);
> print_trailer(s, page, object);
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> }
>
> static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> @@ -818,6 +817,7 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> slab_bug(s, "%s", buf);
> print_page_info(page);
> dump_stack();
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> }
>
> static void init_object(struct kmem_cache *s, void *object, u8 val)
> @@ -869,6 +869,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
> fault, end - 1, fault - addr,
> fault[0], value);
> print_trailer(s, page, object);
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
>
> skip_bug_print:
> restore_bytes(s, what, value, fault, end);
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/slub: Add taint after the errors are printed
2021-06-16 16:34 ` Vlastimil Babka
@ 2021-06-16 22:13 ` Rafael Aquini
0 siblings, 0 replies; 8+ messages in thread
From: Rafael Aquini @ 2021-06-16 22:13 UTC (permalink / raw)
To: Vlastimil Babka
Cc: Georgi Djakov, akpm, iamjoonsoo.kim, rientjes, penberg, cl,
linux-mm, linux-kernel, djakov
On Wed, Jun 16, 2021 at 06:34:41PM +0200, Vlastimil Babka wrote:
> On 6/16/21 6:25 PM, Georgi Djakov wrote:
> > When running the kernel with panic_on_taint, the usual slub debug error
> > messages are not being printed when object corruption happens. That's
> > because we panic in add_taint(), which is called before printing the
> > additional information. This is a bit unfortunate as the error messages
> > are actually very useful, especially before a panic. Let's fix this by
> > moving add_taint() after the errors are printed on the console.
> >
> > Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
>
> Makes sense.
>
> While at it, I wonder if we should use LOCKDEP_STILL_OK instead of
> LOCKDEP_NOW_UNRELIABLE. Isn't it too pessimistic to assume that some slab's
> memory corruption hit some lock state?
>
Given there is noted corruption I don't think it's safe to assume otherwise.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] mm/slub: Add taint after the errors are printed
2021-06-16 16:25 [PATCH] mm/slub: Add taint after the errors are printed Georgi Djakov
2021-06-16 16:34 ` Vlastimil Babka
@ 2021-06-16 22:11 ` Rafael Aquini
2021-06-17 9:22 ` Aaron Tomlin
` (2 subsequent siblings)
4 siblings, 0 replies; 8+ messages in thread
From: Rafael Aquini @ 2021-06-16 22:11 UTC (permalink / raw)
To: Georgi Djakov
Cc: vbabka, akpm, iamjoonsoo.kim, rientjes, penberg, cl, linux-mm,
linux-kernel, djakov
On Wed, Jun 16, 2021 at 09:25:38AM -0700, Georgi Djakov wrote:
> When running the kernel with panic_on_taint, the usual slub debug error
> messages are not being printed when object corruption happens. That's
> because we panic in add_taint(), which is called before printing the
> additional information. This is a bit unfortunate as the error messages
> are actually very useful, especially before a panic. Let's fix this by
> moving add_taint() after the errors are printed on the console.
>
> Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
> ---
> mm/slub.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index a8b0daa1a307..ce7b8e4551b5 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -719,8 +719,6 @@ static void slab_bug(struct kmem_cache *s, char *fmt, ...)
> pr_err("=============================================================================\n");
> pr_err("BUG %s (%s): %pV\n", s->name, print_tainted(), &vaf);
> pr_err("-----------------------------------------------------------------------------\n\n");
> -
> - add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> va_end(args);
> }
>
> @@ -801,6 +799,7 @@ void object_err(struct kmem_cache *s, struct page *page,
>
> slab_bug(s, "%s", reason);
> print_trailer(s, page, object);
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> }
>
> static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> @@ -818,6 +817,7 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> slab_bug(s, "%s", buf);
> print_page_info(page);
> dump_stack();
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> }
>
> static void init_object(struct kmem_cache *s, void *object, u8 val)
> @@ -869,6 +869,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
> fault, end - 1, fault - addr,
> fault[0], value);
> print_trailer(s, page, object);
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
>
> skip_bug_print:
> restore_bytes(s, what, value, fault, end);
>
Acked-by: Rafael Aquini <aquini@redhat.com>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/slub: Add taint after the errors are printed
2021-06-16 16:25 [PATCH] mm/slub: Add taint after the errors are printed Georgi Djakov
2021-06-16 16:34 ` Vlastimil Babka
2021-06-16 22:11 ` Rafael Aquini
@ 2021-06-17 9:22 ` Aaron Tomlin
2021-06-17 14:07 ` Vlastimil Babka
2021-06-18 19:38 ` David Rientjes
4 siblings, 0 replies; 8+ messages in thread
From: Aaron Tomlin @ 2021-06-17 9:22 UTC (permalink / raw)
To: Georgi Djakov
Cc: vbabka, akpm, iamjoonsoo.kim, rientjes, penberg, cl, linux-mm,
linux-kernel, djakov
On Wed 2021-06-16 09:25 -0700, Georgi Djakov wrote:
> When running the kernel with panic_on_taint, the usual slub debug error
> messages are not being printed when object corruption happens. That's
> because we panic in add_taint(), which is called before printing the
> additional information. This is a bit unfortunate as the error messages
> are actually very useful, especially before a panic. Let's fix this by
> moving add_taint() after the errors are printed on the console.
>
> Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
> ---
> mm/slub.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index a8b0daa1a307..ce7b8e4551b5 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -719,8 +719,6 @@ static void slab_bug(struct kmem_cache *s, char *fmt, ...)
> pr_err("=============================================================================\n");
> pr_err("BUG %s (%s): %pV\n", s->name, print_tainted(), &vaf);
> pr_err("-----------------------------------------------------------------------------\n\n");
> -
> - add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> va_end(args);
> }
>
> @@ -801,6 +799,7 @@ void object_err(struct kmem_cache *s, struct page *page,
>
> slab_bug(s, "%s", reason);
> print_trailer(s, page, object);
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> }
>
> static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> @@ -818,6 +817,7 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> slab_bug(s, "%s", buf);
> print_page_info(page);
> dump_stack();
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> }
>
> static void init_object(struct kmem_cache *s, void *object, u8 val)
> @@ -869,6 +869,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
> fault, end - 1, fault - addr,
> fault[0], value);
> print_trailer(s, page, object);
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
>
> skip_bug_print:
> restore_bytes(s, what, value, fault, end);
>
Good catch. Thanks!
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
--
Aaron Tomlin
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/slub: Add taint after the errors are printed
2021-06-16 16:25 [PATCH] mm/slub: Add taint after the errors are printed Georgi Djakov
` (2 preceding siblings ...)
2021-06-17 9:22 ` Aaron Tomlin
@ 2021-06-17 14:07 ` Vlastimil Babka
2021-06-18 19:38 ` David Rientjes
4 siblings, 0 replies; 8+ messages in thread
From: Vlastimil Babka @ 2021-06-17 14:07 UTC (permalink / raw)
To: Georgi Djakov, akpm, iamjoonsoo.kim, rientjes, penberg, cl
Cc: linux-mm, linux-kernel, djakov
On 6/16/21 6:25 PM, Georgi Djakov wrote:
> When running the kernel with panic_on_taint, the usual slub debug error
> messages are not being printed when object corruption happens. That's
> because we panic in add_taint(), which is called before printing the
> additional information. This is a bit unfortunate as the error messages
> are actually very useful, especially before a panic. Let's fix this by
> moving add_taint() after the errors are printed on the console.
>
> Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> mm/slub.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index a8b0daa1a307..ce7b8e4551b5 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -719,8 +719,6 @@ static void slab_bug(struct kmem_cache *s, char *fmt, ...)
> pr_err("=============================================================================\n");
> pr_err("BUG %s (%s): %pV\n", s->name, print_tainted(), &vaf);
> pr_err("-----------------------------------------------------------------------------\n\n");
> -
> - add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> va_end(args);
> }
>
> @@ -801,6 +799,7 @@ void object_err(struct kmem_cache *s, struct page *page,
>
> slab_bug(s, "%s", reason);
> print_trailer(s, page, object);
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> }
>
> static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> @@ -818,6 +817,7 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> slab_bug(s, "%s", buf);
> print_page_info(page);
> dump_stack();
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
> }
>
> static void init_object(struct kmem_cache *s, void *object, u8 val)
> @@ -869,6 +869,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
> fault, end - 1, fault - addr,
> fault[0], value);
> print_trailer(s, page, object);
> + add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
>
> skip_bug_print:
> restore_bytes(s, what, value, fault, end);
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/slub: Add taint after the errors are printed
2021-06-16 16:25 [PATCH] mm/slub: Add taint after the errors are printed Georgi Djakov
@ 2021-06-18 19:38 ` David Rientjes
2021-06-16 22:11 ` Rafael Aquini
` (3 subsequent siblings)
4 siblings, 0 replies; 8+ messages in thread
From: David Rientjes @ 2021-06-18 19:38 UTC (permalink / raw)
To: Georgi Djakov
Cc: vbabka, akpm, iamjoonsoo.kim, penberg, cl, linux-mm,
linux-kernel, djakov
On Wed, 16 Jun 2021, Georgi Djakov wrote:
> When running the kernel with panic_on_taint, the usual slub debug error
> messages are not being printed when object corruption happens. That's
> because we panic in add_taint(), which is called before printing the
> additional information. This is a bit unfortunate as the error messages
> are actually very useful, especially before a panic. Let's fix this by
> moving add_taint() after the errors are printed on the console.
>
> Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
Acked-by: David Rientjes <rientjes@google.com>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] mm/slub: Add taint after the errors are printed
@ 2021-06-18 19:38 ` David Rientjes
0 siblings, 0 replies; 8+ messages in thread
From: David Rientjes @ 2021-06-18 19:38 UTC (permalink / raw)
To: Georgi Djakov
Cc: vbabka, akpm, iamjoonsoo.kim, penberg, cl, linux-mm,
linux-kernel, djakov
On Wed, 16 Jun 2021, Georgi Djakov wrote:
> When running the kernel with panic_on_taint, the usual slub debug error
> messages are not being printed when object corruption happens. That's
> because we panic in add_taint(), which is called before printing the
> additional information. This is a bit unfortunate as the error messages
> are actually very useful, especially before a panic. Let's fix this by
> moving add_taint() after the errors are printed on the console.
>
> Signed-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
Acked-by: David Rientjes <rientjes@google.com>
^ permalink raw reply [flat|nested] 8+ messages in thread