include/linux/slab.h | 1 + include/linux/stackdepot.h | 3 ++- mm/slab.c | 5 +++++ mm/slob.c | 5 +++++ mm/slub.c | 19 ++++++++++++++++--- 5 files changed, 29 insertions(+), 4 deletions(-)
commit ba10d4b46655 ("mm/slub: use stackdepot to save stack trace in
objects") initializes stack depot in cache creation if SLAB_STORE_USER
flag is set.
This can make kernel crash because a cache can be crashed in various
contexts. For example if user sets slub_debug=U, kernel crashes
because create_boot_cache() calls stack_depot_init(), which tries to
allocate hash table using memblock_alloc() if slab is not available.
But memblock is also not available at that time.
This patch solves the problem by initializing stack depot early
in boot process if SLAB_STORE_USER debug flag is set globally
or the flag is set for at least one cache.
[ elver@google.com: initialize stack depot depending on slub_debug
parameter instead of allowing stack_depot_init() to be called
during kmem_cache_init() for simplicity. ]
[ vbabka@suse.cz: parse slub_debug parameter in setup_slub_debug()
and initialize stack depot in stack_depot_early_init(). ]
[ lkp@intel.com: Fix build error. ]
Link: https://lore.kernel.org/all/YhyeaP8lrzKgKm5A@ip-172-31-19-208.ap-northeast-1.compute.internal/
Fixes: ba10d4b46655 ("mm/slub: use stackdepot to save stack trace in objects")
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
include/linux/slab.h | 1 +
include/linux/stackdepot.h | 3 ++-
mm/slab.c | 5 +++++
mm/slob.c | 5 +++++
mm/slub.c | 19 ++++++++++++++++---
5 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 37bde99b74af..d2b0f8f9e5e6 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -762,6 +762,7 @@ extern void kvfree_sensitive(const void *addr, size_t len);
unsigned int kmem_cache_size(struct kmem_cache *s);
void __init kmem_cache_init_late(void);
+int __init slab_stack_depot_init(void);
#if defined(CONFIG_SMP) && defined(CONFIG_SLAB)
int slab_prepare_cpu(unsigned int cpu);
diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index 17f992fe6355..a813a2673c48 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -12,6 +12,7 @@
#define _LINUX_STACKDEPOT_H
#include <linux/gfp.h>
+#include <linux/slab.h>
typedef u32 depot_stack_handle_t;
@@ -32,7 +33,7 @@ int stack_depot_init(void);
#ifdef CONFIG_STACKDEPOT_ALWAYS_INIT
static inline int stack_depot_early_init(void) { return stack_depot_init(); }
#else
-static inline int stack_depot_early_init(void) { return 0; }
+static inline int stack_depot_early_init(void) { return slab_stack_depot_init(); }
#endif
depot_stack_handle_t stack_depot_save(unsigned long *entries,
diff --git a/mm/slab.c b/mm/slab.c
index ddf5737c63d9..c7f929665fbe 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1196,6 +1196,11 @@ static void __init set_up_node(struct kmem_cache *cachep, int index)
}
}
+int __init slab_stack_depot_init(void)
+{
+ return 0;
+}
+
/*
* Initialisation. Called after the page allocator have been initialised and
* before smp_init().
diff --git a/mm/slob.c b/mm/slob.c
index 60c5842215f1..7597c219f061 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -725,3 +725,8 @@ void __init kmem_cache_init_late(void)
{
slab_state = FULL;
}
+
+int __init slab_stack_depot_init(void)
+{
+ return 0;
+}
diff --git a/mm/slub.c b/mm/slub.c
index a74afe59a403..8f130f917977 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -646,6 +646,16 @@ static slab_flags_t slub_debug;
static char *slub_debug_string;
static int disable_higher_order_debug;
+static bool __initdata init_stack_depot;
+
+int __init slab_stack_depot_init(void)
+{
+#ifdef CONFIG_STACKDEPOT
+ if (init_stack_depot)
+ stack_depot_init();
+#endif
+ return 0;
+}
/*
* slub is about to manipulate internal object metadata. This memory lies
@@ -1531,6 +1541,8 @@ static int __init setup_slub_debug(char *str)
global_slub_debug_changed = true;
} else {
slab_list_specified = true;
+ if (flags & SLAB_STORE_USER)
+ init_stack_depot = true;
}
}
@@ -1546,6 +1558,10 @@ static int __init setup_slub_debug(char *str)
global_flags = slub_debug;
slub_debug_string = saved_str;
}
+
+ if (global_flags & SLAB_STORE_USER)
+ init_stack_depot = true;
+
out:
slub_debug = global_flags;
if (slub_debug != 0 || slub_debug_string)
@@ -4221,9 +4237,6 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
s->remote_node_defrag_ratio = 1000;
#endif
- if (s->flags & SLAB_STORE_USER && IS_ENABLED(CONFIG_STACKDEPOT))
- stack_depot_init();
-
/* Initialize the pre-computed randomized freelist if slab is up */
if (slab_state >= UP) {
if (init_cache_random_seq(s))
--
2.33.1On 3/1/22 09:51, Hyeonggon Yoo wrote:
> commit ba10d4b46655 ("mm/slub: use stackdepot to save stack trace in
> objects") initializes stack depot in cache creation if SLAB_STORE_USER
> flag is set.
As pointed out, this is not a stable commit, the series was just posted for
review and there will be v2. So instead of "this fixes the commit..." I
suggest writing the patch assuming it's a preparation for the patch
"mm/slub: use stackdepot"... and I can then make it part of the series.
So it should instead explain that for slub_debug we will need a way to
trigger stack_depot_early_init() based on boot options and so this patch
introduces it...
> This can make kernel crash because a cache can be crashed in various
> contexts. For example if user sets slub_debug=U, kernel crashes
> because create_boot_cache() calls stack_depot_init(), which tries to
> allocate hash table using memblock_alloc() if slab is not available.
> But memblock is also not available at that time.
>
> This patch solves the problem by initializing stack depot early
> in boot process if SLAB_STORE_USER debug flag is set globally
> or the flag is set for at least one cache.
>
> [ elver@google.com: initialize stack depot depending on slub_debug
> parameter instead of allowing stack_depot_init() to be called
> during kmem_cache_init() for simplicity. ]
>
> [ vbabka@suse.cz: parse slub_debug parameter in setup_slub_debug()
> and initialize stack depot in stack_depot_early_init(). ]
>
> [ lkp@intel.com: Fix build error. ]
>
> Link: https://lore.kernel.org/all/YhyeaP8lrzKgKm5A@ip-172-31-19-208.ap-northeast-1.compute.internal/
> Fixes: ba10d4b46655 ("mm/slub: use stackdepot to save stack trace in objects")
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> ---
> include/linux/slab.h | 1 +
> include/linux/stackdepot.h | 3 ++-
> mm/slab.c | 5 +++++
> mm/slob.c | 5 +++++
> mm/slub.c | 19 ++++++++++++++++---
> 5 files changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 37bde99b74af..d2b0f8f9e5e6 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -762,6 +762,7 @@ extern void kvfree_sensitive(const void *addr, size_t len);
>
> unsigned int kmem_cache_size(struct kmem_cache *s);
> void __init kmem_cache_init_late(void);
> +int __init slab_stack_depot_init(void);
>
> #if defined(CONFIG_SMP) && defined(CONFIG_SLAB)
> int slab_prepare_cpu(unsigned int cpu);
> diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
> index 17f992fe6355..a813a2673c48 100644
> --- a/include/linux/stackdepot.h
> +++ b/include/linux/stackdepot.h
> @@ -12,6 +12,7 @@
> #define _LINUX_STACKDEPOT_H
>
> #include <linux/gfp.h>
> +#include <linux/slab.h>
>
> typedef u32 depot_stack_handle_t;
>
> @@ -32,7 +33,7 @@ int stack_depot_init(void);
> #ifdef CONFIG_STACKDEPOT_ALWAYS_INIT
> static inline int stack_depot_early_init(void) { return stack_depot_init(); }
> #else
> -static inline int stack_depot_early_init(void) { return 0; }
> +static inline int stack_depot_early_init(void) { return slab_stack_depot_init(); }
> #endif
I think the approach should be generic for stackdepot, not tied to a
function that belongs to slab with 3 different implementations.
E.g. in stackdepot.h declare a variable e.g. "stack_depot_want_early_init"
that is checked in stack_depot_early_init() above to call stack_depot_init().
> depot_stack_handle_t stack_depot_save(unsigned long *entries,
> diff --git a/mm/slab.c b/mm/slab.c
> index ddf5737c63d9..c7f929665fbe 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -1196,6 +1196,11 @@ static void __init set_up_node(struct kmem_cache *cachep, int index)
> }
> }
>
> +int __init slab_stack_depot_init(void)
> +{
> + return 0;
> +}
> +
> /*
> * Initialisation. Called after the page allocator have been initialised and
> * before smp_init().
> diff --git a/mm/slob.c b/mm/slob.c
> index 60c5842215f1..7597c219f061 100644
> --- a/mm/slob.c
> +++ b/mm/slob.c
> @@ -725,3 +725,8 @@ void __init kmem_cache_init_late(void)
> {
> slab_state = FULL;
> }
> +
> +int __init slab_stack_depot_init(void)
> +{
> + return 0;
> +}
> diff --git a/mm/slub.c b/mm/slub.c
> index a74afe59a403..8f130f917977 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -646,6 +646,16 @@ static slab_flags_t slub_debug;
>
> static char *slub_debug_string;
> static int disable_higher_order_debug;
> +static bool __initdata init_stack_depot;
> +
> +int __init slab_stack_depot_init(void)
> +{
> +#ifdef CONFIG_STACKDEPOT
> + if (init_stack_depot)
> + stack_depot_init();
> +#endif
> + return 0;
> +}
> /*
> * slub is about to manipulate internal object metadata. This memory lies
> @@ -1531,6 +1541,8 @@ static int __init setup_slub_debug(char *str)
> global_slub_debug_changed = true;
> } else {
> slab_list_specified = true;
> + if (flags & SLAB_STORE_USER)
> + init_stack_depot = true;
> }
> }
>
> @@ -1546,6 +1558,10 @@ static int __init setup_slub_debug(char *str)
> global_flags = slub_debug;
> slub_debug_string = saved_str;
> }
> +
> + if (global_flags & SLAB_STORE_USER)
> + init_stack_depot = true;
This looks good, it would just set the "stack_depot_want_early_init"
variable instead. But logically should be part of "mm/slub: use
stackdepot...", not part of patch that introduces the variable. That so if
you don't mind I would move it there with credit.
> out:
> slub_debug = global_flags;
> if (slub_debug != 0 || slub_debug_string)
> @@ -4221,9 +4237,6 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
> s->remote_node_defrag_ratio = 1000;
> #endif
>
> - if (s->flags & SLAB_STORE_USER && IS_ENABLED(CONFIG_STACKDEPOT))
> - stack_depot_init();
> -
> /* Initialize the pre-computed randomized freelist if slab is up */
> if (slab_state >= UP) {
> if (init_cache_random_seq(s))
On Tue, Mar 01, 2022 at 10:14:30AM +0100, Vlastimil Babka wrote:
> On 3/1/22 09:51, Hyeonggon Yoo wrote:
> > commit ba10d4b46655 ("mm/slub: use stackdepot to save stack trace in
> > objects") initializes stack depot in cache creation if SLAB_STORE_USER
> > flag is set.
>
> As pointed out, this is not a stable commit, the series was just posted for
> review and there will be v2. So instead of "this fixes the commit..." I
> suggest writing the patch assuming it's a preparation for the patch
> "mm/slub: use stackdepot"... and I can then make it part of the series.
> So it should instead explain that for slub_debug we will need a way to
> trigger stack_depot_early_init() based on boot options and so this patch
> introduces it...
>
Agreed.
> > This can make kernel crash because a cache can be crashed in various
> > contexts. For example if user sets slub_debug=U, kernel crashes
> > because create_boot_cache() calls stack_depot_init(), which tries to
> > allocate hash table using memblock_alloc() if slab is not available.
> > But memblock is also not available at that time.
> >
> > This patch solves the problem by initializing stack depot early
> > in boot process if SLAB_STORE_USER debug flag is set globally
> > or the flag is set for at least one cache.
> >
> > [ elver@google.com: initialize stack depot depending on slub_debug
> > parameter instead of allowing stack_depot_init() to be called
> > during kmem_cache_init() for simplicity. ]
> >
> > [ vbabka@suse.cz: parse slub_debug parameter in setup_slub_debug()
> > and initialize stack depot in stack_depot_early_init(). ]
> >
> > [ lkp@intel.com: Fix build error. ]
> >
> > Link: https://lore.kernel.org/all/YhyeaP8lrzKgKm5A@ip-172-31-19-208.ap-northeast-1.compute.internal/
> > Fixes: ba10d4b46655 ("mm/slub: use stackdepot to save stack trace in objects")
> > Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> > ---
> > include/linux/slab.h | 1 +
> > include/linux/stackdepot.h | 3 ++-
> > mm/slab.c | 5 +++++
> > mm/slob.c | 5 +++++
> > mm/slub.c | 19 ++++++++++++++++---
> > 5 files changed, 29 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index 37bde99b74af..d2b0f8f9e5e6 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -762,6 +762,7 @@ extern void kvfree_sensitive(const void *addr, size_t len);
> >
> > unsigned int kmem_cache_size(struct kmem_cache *s);
> > void __init kmem_cache_init_late(void);
> > +int __init slab_stack_depot_init(void);
> >
> > #if defined(CONFIG_SMP) && defined(CONFIG_SLAB)
> > int slab_prepare_cpu(unsigned int cpu);
> > diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
> > index 17f992fe6355..a813a2673c48 100644
> > --- a/include/linux/stackdepot.h
> > +++ b/include/linux/stackdepot.h
> > @@ -12,6 +12,7 @@
> > #define _LINUX_STACKDEPOT_H
> >
> > #include <linux/gfp.h>
> > +#include <linux/slab.h>
> >
> > typedef u32 depot_stack_handle_t;
> >
> > @@ -32,7 +33,7 @@ int stack_depot_init(void);
> > #ifdef CONFIG_STACKDEPOT_ALWAYS_INIT
> > static inline int stack_depot_early_init(void) { return stack_depot_init(); }
> > #else
> > -static inline int stack_depot_early_init(void) { return 0; }
> > +static inline int stack_depot_early_init(void) { return slab_stack_depot_init(); }
> > #endif
>
> I think the approach should be generic for stackdepot, not tied to a
> function that belongs to slab with 3 different implementations.
> E.g. in stackdepot.h declare a variable e.g. "stack_depot_want_early_init"
> that is checked in stack_depot_early_init() above to call stack_depot_init().
Hmm yeah if we define it in stack depot, that would be nice.
I just didn't want to expose global variable that is specific to slub.
> > depot_stack_handle_t stack_depot_save(unsigned long *entries,
> > diff --git a/mm/slab.c b/mm/slab.c
> > index ddf5737c63d9..c7f929665fbe 100644
> > --- a/mm/slab.c
> > +++ b/mm/slab.c
> > @@ -1196,6 +1196,11 @@ static void __init set_up_node(struct kmem_cache *cachep, int index)
> > }
> > }
> >
> > +int __init slab_stack_depot_init(void)
> > +{
> > + return 0;
> > +}
> > +
> > /*
> > * Initialisation. Called after the page allocator have been initialised and
> > * before smp_init().
> > diff --git a/mm/slob.c b/mm/slob.c
> > index 60c5842215f1..7597c219f061 100644
> > --- a/mm/slob.c
> > +++ b/mm/slob.c
> > @@ -725,3 +725,8 @@ void __init kmem_cache_init_late(void)
> > {
> > slab_state = FULL;
> > }
> > +
> > +int __init slab_stack_depot_init(void)
> > +{
> > + return 0;
> > +}
> > diff --git a/mm/slub.c b/mm/slub.c
> > index a74afe59a403..8f130f917977 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -646,6 +646,16 @@ static slab_flags_t slub_debug;
> >
> > static char *slub_debug_string;
> > static int disable_higher_order_debug;
> > +static bool __initdata init_stack_depot;
> > +
> > +int __init slab_stack_depot_init(void)
> > +{
> > +#ifdef CONFIG_STACKDEPOT
> > + if (init_stack_depot)
> > + stack_depot_init();
> > +#endif
> > + return 0;
> > +}
>
>
>
> > /*
> > * slub is about to manipulate internal object metadata. This memory lies
> > @@ -1531,6 +1541,8 @@ static int __init setup_slub_debug(char *str)
> > global_slub_debug_changed = true;
> > } else {
> > slab_list_specified = true;
> > + if (flags & SLAB_STORE_USER)
> > + init_stack_depot = true;
> > }
> > }
> >
> > @@ -1546,6 +1558,10 @@ static int __init setup_slub_debug(char *str)
> > global_flags = slub_debug;
> > slub_debug_string = saved_str;
> > }
> > +
> > + if (global_flags & SLAB_STORE_USER)
> > + init_stack_depot = true;
>
> This looks good, it would just set the "stack_depot_want_early_init"
> variable instead. But logically should be part of "mm/slub: use
> stackdepot...", not part of patch that introduces the variable. That so if
> you don't mind I would move it there with credit.
>
Oh I don't mind that.
Then I will expect this to be solved in next series...
I'm looking forward to next version. Thanks!
--
Thank you, You are awesome!
Hyeonggon :-)
> > out:
> > slub_debug = global_flags;
> > if (slub_debug != 0 || slub_debug_string)
> > @@ -4221,9 +4237,6 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
> > s->remote_node_defrag_ratio = 1000;
> > #endif
> >
> > - if (s->flags & SLAB_STORE_USER && IS_ENABLED(CONFIG_STACKDEPOT))
> > - stack_depot_init();
> > -
> > /* Initialize the pre-computed randomized freelist if slab is up */
> > if (slab_state >= UP) {
> > if (init_cache_random_seq(s))
>
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