The patch titled
Subject: mm, slub: make remaining slub_debug related attributes read-only
has been added to the -mm tree. Its filename is
mm-slub-make-remaining-slub_debug-related-attributes-read-only.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-slub-make-remaining-slub_debug-related-attributes-read-only.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-make-remaining-slub_debug-related-attributes-read-only.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm, slub: make remaining slub_debug related attributes read-only
SLUB_DEBUG creates several files under /sys/kernel/slab/<cache>/ that can
be read to check if the respective debugging options are enabled for given
cache. Some options, namely sanity_checks, trace, and failslab can be
also enabled and disabled at runtime by writing into the files.
The runtime toggling is racy. Some options disable __CMPXCHG_DOUBLE when
enabled, which means that in case of concurrent allocations, some can
still use __CMPXCHG_DOUBLE and some not, leading to potential corruption.
The s->flags field is also not updated or checked atomically. The
simplest solution is to remove the runtime toggling. The extended
slub_debug boot parameter syntax introduced by earlier patch should allow
to fine-tune the debugging configuration during boot with same
granularity.
Link: http://lkml.kernel.org/r/20200610163135.17364-5-vbabka@xxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/slub.rst | 7 +---
mm/slub.c | 62 +-----------------------------------
2 files changed, 5 insertions(+), 64 deletions(-)
--- a/Documentation/vm/slub.rst~mm-slub-make-remaining-slub_debug-related-attributes-read-only
+++ a/Documentation/vm/slub.rst
@@ -116,11 +116,8 @@ options from the ``slub_debug`` paramete
T trace
A failslab
-The sanity_checks, trace and failslab files are writable, so writing 1 or 0
-will enable or disable the option at runtime. The writes to trace and failslab
-may return -EINVAL if the cache is subject to slab merging. Careful with
-tracing: It may spew out lots of information and never stop if used on the
-wrong slab.
+Careful with tracing: It may spew out lots of information and never stop if
+used on the wrong slab.
Slab merging
============
--- a/mm/slub.c~mm-slub-make-remaining-slub_debug-related-attributes-read-only
+++ a/mm/slub.c
@@ -5056,20 +5056,6 @@ static ssize_t show_slab_objects(struct
return x + sprintf(buf + x, "\n");
}
-#ifdef CONFIG_SLUB_DEBUG
-static int any_slab_objects(struct kmem_cache *s)
-{
- int node;
- struct kmem_cache_node *n;
-
- for_each_kmem_cache_node(s, node, n)
- if (atomic_long_read(&n->total_objects))
- return 1;
-
- return 0;
-}
-#endif
-
#define to_slab_attr(n) container_of(n, struct slab_attribute, attr)
#define to_slab(n) container_of(n, struct kmem_cache, kobj)
@@ -5291,43 +5277,13 @@ static ssize_t sanity_checks_show(struct
{
return sprintf(buf, "%d\n", !!(s->flags & SLAB_CONSISTENCY_CHECKS));
}
-
-static ssize_t sanity_checks_store(struct kmem_cache *s,
- const char *buf, size_t length)
-{
- s->flags &= ~SLAB_CONSISTENCY_CHECKS;
- if (buf[0] == '1') {
- s->flags &= ~__CMPXCHG_DOUBLE;
- s->flags |= SLAB_CONSISTENCY_CHECKS;
- }
- return length;
-}
-SLAB_ATTR(sanity_checks);
+SLAB_ATTR_RO(sanity_checks);
static ssize_t trace_show(struct kmem_cache *s, char *buf)
{
return sprintf(buf, "%d\n", !!(s->flags & SLAB_TRACE));
}
-
-static ssize_t trace_store(struct kmem_cache *s, const char *buf,
- size_t length)
-{
- /*
- * Tracing a merged cache is going to give confusing results
- * as well as cause other issues like converting a mergeable
- * cache into an umergeable one.
- */
- if (s->refcount > 1)
- return -EINVAL;
-
- s->flags &= ~SLAB_TRACE;
- if (buf[0] == '1') {
- s->flags &= ~__CMPXCHG_DOUBLE;
- s->flags |= SLAB_TRACE;
- }
- return length;
-}
-SLAB_ATTR(trace);
+SLAB_ATTR_RO(trace);
static ssize_t red_zone_show(struct kmem_cache *s, char *buf)
{
@@ -5391,19 +5347,7 @@ static ssize_t failslab_show(struct kmem
{
return sprintf(buf, "%d\n", !!(s->flags & SLAB_FAILSLAB));
}
-
-static ssize_t failslab_store(struct kmem_cache *s, const char *buf,
- size_t length)
-{
- if (s->refcount > 1)
- return -EINVAL;
-
- s->flags &= ~SLAB_FAILSLAB;
- if (buf[0] == '1')
- s->flags |= SLAB_FAILSLAB;
- return length;
-}
-SLAB_ATTR(failslab);
+SLAB_ATTR_RO(failslab);
#endif
static ssize_t shrink_show(struct kmem_cache *s, char *buf)
_
Patches currently in -mm which might be from vbabka@xxxxxxx are
mm-slub-extend-slub_debug-syntax-for-multiple-blocks.patch
mm-slub-make-some-slub_debug-related-attributes-read-only.patch
mm-slub-remove-runtime-allocation-order-changes.patch
mm-slub-make-remaining-slub_debug-related-attributes-read-only.patch
mm-slub-make-reclaim_account-attribute-read-only.patch
mm-slub-introduce-static-key-for-slub_debug.patch
mm-slub-introduce-kmem_cache_debug_flags.patch
mm-slub-extend-checks-guarded-by-slub_debug-static-key.patch
mm-slab-slub-move-and-improve-cache_from_obj.patch
