The patch titled
lib/idr.c: fix rcu related race with idr_find
has been removed from the -mm tree. Its filename was
lib-idrc-fix-rcu-related-race-with-idr_find.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: lib/idr.c: fix rcu related race with idr_find
From: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
2nd part of the fixes needed for
http://bugzilla.kernel.org/show_bug.cgi?id=11796.
When the idr tree is either grown or shrunk, then the update to the number
of layers and the top pointer were not atomic. This race caused crashes.
The attached patch fixes that by replicating the layers counter in each
layer, thus idr_find doesn't need idp->layers anymore.
Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: Clement Calmels <cboulte@xxxxxxxxx>
Cc: Nadia Derbey <Nadia.Derbey@xxxxxxxx>
Cc: Pierre Peiffer <peifferp@xxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/idr.h | 3 ++-
lib/idr.c | 14 ++++++++++++--
2 files changed, 14 insertions(+), 3 deletions(-)
diff -puN include/linux/idr.h~lib-idrc-fix-rcu-related-race-with-idr_find include/linux/idr.h
--- a/include/linux/idr.h~lib-idrc-fix-rcu-related-race-with-idr_find
+++ a/include/linux/idr.h
@@ -52,13 +52,14 @@ struct idr_layer {
unsigned long bitmap; /* A zero bit means "space here" */
struct idr_layer *ary[1<<IDR_BITS];
int count; /* When zero, we can release it */
+ int layer; /* distance from leaf */
struct rcu_head rcu_head;
};
struct idr {
struct idr_layer *top;
struct idr_layer *id_free;
- int layers;
+ int layers; /* only valid without concurrent changes */
int id_free_cnt;
spinlock_t lock;
};
diff -puN lib/idr.c~lib-idrc-fix-rcu-related-race-with-idr_find lib/idr.c
--- a/lib/idr.c~lib-idrc-fix-rcu-related-race-with-idr_find
+++ a/lib/idr.c
@@ -185,6 +185,7 @@ static int sub_alloc(struct idr *idp, in
new = get_from_free_list(idp);
if (!new)
return -1;
+ new->layer = l-1;
rcu_assign_pointer(p->ary[m], new);
p->count++;
}
@@ -210,6 +211,7 @@ build_up:
if (unlikely(!p)) {
if (!(p = get_from_free_list(idp)))
return -1;
+ p->layer = 0;
layers = 1;
}
/*
@@ -237,6 +239,7 @@ build_up:
}
new->ary[0] = p;
new->count = 1;
+ new->layer = layers-1;
if (p->bitmap == IDR_FULL)
__set_bit(0, &new->bitmap);
p = new;
@@ -493,17 +496,21 @@ void *idr_find(struct idr *idp, int id)
int n;
struct idr_layer *p;
- n = idp->layers * IDR_BITS;
p = rcu_dereference(idp->top);
+ if (!p)
+ return NULL;
+ n = (p->layer+1) * IDR_BITS;
/* Mask off upper bits we don't use for the search. */
id &= MAX_ID_MASK;
if (id >= (1 << n))
return NULL;
+ BUG_ON(n == 0);
while (n > 0 && p) {
n -= IDR_BITS;
+ BUG_ON(n != p->layer*IDR_BITS);
p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
}
return((void *)p);
@@ -582,8 +589,11 @@ void *idr_replace(struct idr *idp, void
int n;
struct idr_layer *p, *old_p;
- n = idp->layers * IDR_BITS;
p = idp->top;
+ if (!p)
+ return ERR_PTR(-EINVAL);
+
+ n = (p->layer+1) * IDR_BITS;
id &= MAX_ID_MASK;
_
Patches currently in -mm which might be from manfred@xxxxxxxxxxxxxxxx are
repeatable-slab-corruption-with-ltp-msgctl08.patch
mm-debug-dump-pageframes-on-bad_page.patch
slab-leaks3-default-y.patch
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