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authorVlastimil Babka <vbabka@suse.cz>2020-08-06 23:18:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-07 11:33:22 -0700
commit060807f841ac94d3826ce6fa3b4f3831cd0c015b (patch)
tree7fb9985e561e2d1ae304ca222c250ca9eab1654d
parent32a6f409b6935d175464f26d31250ea13fda6b66 (diff)
downloadlinux-060807f841ac94d3826ce6fa3b4f3831cd0c015b.tar.bz2
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. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Roman Gushchin <guro@fb.com> Cc: Christoph Lameter <cl@linux.com> Cc: Jann Horn <jannh@google.com> Cc: Vijayanand Jitta <vjitta@codeaurora.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Pekka Enberg <penberg@kernel.org> Link: http://lkml.kernel.org/r/20200610163135.17364-5-vbabka@suse.cz Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/vm/slub.rst7
-rw-r--r--mm/slub.c62
2 files changed, 5 insertions, 64 deletions
diff --git a/Documentation/vm/slub.rst b/Documentation/vm/slub.rst
index 36241dfba024..289d231cee97 100644
--- a/Documentation/vm/slub.rst
+++ b/Documentation/vm/slub.rst
@@ -116,11 +116,8 @@ options from the ``slub_debug`` parameter translate to the following files::
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
============
diff --git a/mm/slub.c b/mm/slub.c
index f03b1073bdcf..5848b7c3575a 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5040,20 +5040,6 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
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)
@@ -5275,43 +5261,13 @@ static ssize_t sanity_checks_show(struct kmem_cache *s, char *buf)
{
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)
{
@@ -5375,19 +5331,7 @@ static ssize_t failslab_show(struct kmem_cache *s, char *buf)
{
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)