From: <gregkh@linuxfoundation.org>
To: surenb@google.com, akpm@linux-foundation.org, brauner@kernel.org,
caoxiaofeng@yulong.com, ccross@google.com,
chris.hyser@oracle.com, dave.hansen@intel.com, dave@stgolabs.net,
david@redhat.com, ebiederm@xmission.com, gorcunov@gmail.com,
hannes@cmpxchg.org, keescook@chromium.org,
kirill.shutemov@linux.intel.com, legion@kernel.org,
mhocko@suse.com, pcc@google.com, sashal@kernel.org,
sumit.semwal@linaro.org, torvalds@linux-foundation.org,
vbabka@suse.cz, willy@infradead.org
Cc: <stable@vger.kernel.org>
Subject: FAILED: patch "[PATCH] mm: prevent vm_area_struct::anon_name refcount saturation" failed to apply to 5.15-stable tree
Date: Sun, 06 Mar 2022 10:37:21 +0100 [thread overview]
Message-ID: <1646559441105125@kroah.com> (raw)
The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 96403e11283def1d1c465c8279514c9a504d8630 Mon Sep 17 00:00:00 2001
From: Suren Baghdasaryan <surenb@google.com>
Date: Fri, 4 Mar 2022 20:28:55 -0800
Subject: [PATCH] mm: prevent vm_area_struct::anon_name refcount saturation
A deep process chain with many vmas could grow really high. With
default sysctl_max_map_count (64k) and default pid_max (32k) the max
number of vmas in the system is 2147450880 and the refcounter has
headroom of 1073774592 before it reaches REFCOUNT_SATURATED
(3221225472).
Therefore it's unlikely that an anonymous name refcounter will overflow
with these defaults. Currently the max for pid_max is PID_MAX_LIMIT
(4194304) and for sysctl_max_map_count it's INT_MAX (2147483647). In
this configuration anon_vma_name refcount overflow becomes theoretically
possible (that still require heavy sharing of that anon_vma_name between
processes).
kref refcounting interface used in anon_vma_name structure will detect a
counter overflow when it reaches REFCOUNT_SATURATED value but will only
generate a warning and freeze the ref counter. This would lead to the
refcounted object never being freed. A determined attacker could leak
memory like that but it would be rather expensive and inefficient way to
do so.
To ensure anon_vma_name refcount does not overflow, stop anon_vma_name
sharing when the refcount reaches REFCOUNT_MAX (2147483647), which still
leaves INT_MAX/2 (1073741823) values before the counter reaches
REFCOUNT_SATURATED. This should provide enough headroom for raising the
refcounts temporarily.
Link: https://lkml.kernel.org/r/20220223153613.835563-2-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Alexey Gladkov <legion@kernel.org>
Cc: Chris Hyser <chris.hyser@oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Colin Cross <ccross@google.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xiaofeng Cao <caoxiaofeng@yulong.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index dd3accaa4e6d..cf90b1fa2c60 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -161,15 +161,25 @@ static inline void anon_vma_name_put(struct anon_vma_name *anon_name)
kref_put(&anon_name->kref, anon_vma_name_free);
}
+static inline
+struct anon_vma_name *anon_vma_name_reuse(struct anon_vma_name *anon_name)
+{
+ /* Prevent anon_name refcount saturation early on */
+ if (kref_read(&anon_name->kref) < REFCOUNT_MAX) {
+ anon_vma_name_get(anon_name);
+ return anon_name;
+
+ }
+ return anon_vma_name_alloc(anon_name->name);
+}
+
static inline void dup_anon_vma_name(struct vm_area_struct *orig_vma,
struct vm_area_struct *new_vma)
{
struct anon_vma_name *anon_name = anon_vma_name(orig_vma);
- if (anon_name) {
- anon_vma_name_get(anon_name);
- new_vma->anon_name = anon_name;
- }
+ if (anon_name)
+ new_vma->anon_name = anon_vma_name_reuse(anon_name);
}
static inline void free_anon_vma_name(struct vm_area_struct *vma)
diff --git a/mm/madvise.c b/mm/madvise.c
index 081b1cded21e..1f2693dccf7b 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -113,8 +113,7 @@ static int replace_anon_vma_name(struct vm_area_struct *vma,
if (anon_vma_name_eq(orig_name, anon_name))
return 0;
- anon_vma_name_get(anon_name);
- vma->anon_name = anon_name;
+ vma->anon_name = anon_vma_name_reuse(anon_name);
anon_vma_name_put(orig_name);
return 0;
next reply other threads:[~2022-03-06 9:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-06 9:37 gregkh [this message]
2022-03-06 21:50 ` FAILED: patch "[PATCH] mm: prevent vm_area_struct::anon_name refcount saturation" failed to apply to 5.15-stable tree Sasha Levin
2022-03-06 21:58 ` Greg KH
2022-03-06 22:53 ` Suren Baghdasaryan
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