140 lines
4.9 KiB
Diff
140 lines
4.9 KiB
Diff
From cbfc35a48609ceac978791e3ab9dde0c01f8cb20 Mon Sep 17 00:00:00 2001
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From: Waiman Long <longman@redhat.com>
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Date: Thu, 7 May 2020 18:36:06 -0700
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Subject: [PATCH] mm/slub: fix incorrect interpretation of s->offset
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In a couple of places in the slub memory allocator, the code uses
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"s->offset" as a check to see if the free pointer is put right after the
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object. That check is no longer true with commit 3202fa62fb43 ("slub:
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relocate freelist pointer to middle of object").
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As a result, echoing "1" into the validate sysfs file, e.g. of dentry,
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may cause a bunch of "Freepointer corrupt" error reports like the
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following to appear with the system in panic afterwards.
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=============================================================================
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BUG dentry(666:pmcd.service) (Tainted: G B): Freepointer corrupt
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-----------------------------------------------------------------------------
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To fix it, use the check "s->offset == s->inuse" in the new helper
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function freeptr_outside_object() instead. Also add another helper
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function get_info_end() to return the end of info block (inuse + free
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pointer if not overlapping with object).
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Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object")
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Signed-off-by: Waiman Long <longman@redhat.com>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
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Reviewed-by: Kees Cook <keescook@chromium.org>
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Acked-by: Rafael Aquini <aquini@redhat.com>
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Cc: Christoph Lameter <cl@linux.com>
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Cc: Vitaly Nikolenko <vnik@duasynt.com>
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Cc: Silvio Cesare <silvio.cesare@gmail.com>
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Cc: Pekka Enberg <penberg@kernel.org>
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Cc: David Rientjes <rientjes@google.com>
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Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
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Cc: Markus Elfring <Markus.Elfring@web.de>
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Cc: Changbin Du <changbin.du@gmail.com>
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Link: http://lkml.kernel.org/r/20200429135328.26976-1-longman@redhat.com
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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mm/slub.c | 45 ++++++++++++++++++++++++++++++---------------
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1 file changed, 30 insertions(+), 15 deletions(-)
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diff --git a/mm/slub.c b/mm/slub.c
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index 9bf44955c4f1e4..b762450fc9f076 100644
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--- a/mm/slub.c
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+++ b/mm/slub.c
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@@ -551,15 +551,32 @@ static void print_section(char *level, char *text, u8 *addr,
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metadata_access_disable();
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}
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+/*
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+ * See comment in calculate_sizes().
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+ */
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+static inline bool freeptr_outside_object(struct kmem_cache *s)
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+{
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+ return s->offset >= s->inuse;
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+}
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+
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+/*
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+ * Return offset of the end of info block which is inuse + free pointer if
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+ * not overlapping with object.
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+ */
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+static inline unsigned int get_info_end(struct kmem_cache *s)
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+{
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+ if (freeptr_outside_object(s))
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+ return s->inuse + sizeof(void *);
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+ else
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+ return s->inuse;
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+}
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+
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static struct track *get_track(struct kmem_cache *s, void *object,
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enum track_item alloc)
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{
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struct track *p;
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- if (s->offset)
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- p = object + s->offset + sizeof(void *);
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- else
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- p = object + s->inuse;
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+ p = object + get_info_end(s);
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return p + alloc;
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}
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@@ -686,10 +703,7 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
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print_section(KERN_ERR, "Redzone ", p + s->object_size,
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s->inuse - s->object_size);
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- if (s->offset)
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- off = s->offset + sizeof(void *);
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- else
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- off = s->inuse;
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+ off = get_info_end(s);
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if (s->flags & SLAB_STORE_USER)
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off += 2 * sizeof(struct track);
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@@ -782,7 +796,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
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* object address
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* Bytes of the object to be managed.
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* If the freepointer may overlay the object then the free
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- * pointer is the first word of the object.
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+ * pointer is at the middle of the object.
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*
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* Poisoning uses 0x6b (POISON_FREE) and the last byte is
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* 0xa5 (POISON_END)
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@@ -816,11 +830,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
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static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p)
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{
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- unsigned long off = s->inuse; /* The end of info */
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-
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- if (s->offset)
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- /* Freepointer is placed after the object. */
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- off += sizeof(void *);
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+ unsigned long off = get_info_end(s); /* The end of info */
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if (s->flags & SLAB_STORE_USER)
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/* We also have user information there */
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@@ -907,7 +917,7 @@ static int check_object(struct kmem_cache *s, struct page *page,
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check_pad_bytes(s, page, p);
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}
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- if (!s->offset && val == SLUB_RED_ACTIVE)
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+ if (!freeptr_outside_object(s) && val == SLUB_RED_ACTIVE)
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/*
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* Object and freepointer overlap. Cannot check
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* freepointer while object is allocated.
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@@ -3587,6 +3597,11 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
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*
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* This is the case if we do RCU, have a constructor or
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* destructor or are poisoning the objects.
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+ *
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+ * The assumption that s->offset >= s->inuse means free
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+ * pointer is outside of the object is used in the
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+ * freeptr_outside_object() function. If that is no
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+ * longer true, the function needs to be modified.
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*/
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s->offset = size;
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size += sizeof(void *);
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