The patch titled
Subject: lib/idr.c: fix out-of-bounds pointer dereference
has been added to the -mm tree. Its filename is
lib-idr-fix-out-of-bounds-pointer-dereference.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-idr-fix-out-of-bounds-pointer-dereference.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-idr-fix-out-of-bounds-pointer-dereference.patch
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------------------------------------------------------
From: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
Subject: lib/idr.c: fix out-of-bounds pointer dereference
I'm working on address sanitizer project for kernel. Recently we started
experiments with stack instrumentation, to detect out-of-bounds read/write
bugs on stack.
Just after booting I've hit out-of-bounds read on stack in idr_for_each
(and in __idr_remove_all as well):
struct idr_layer **paa = &pa[0];
while (id >= 0 && id <= max) {
...
while (n < fls(id)) {
n += IDR_BITS;
p = *--paa; <--- here we are reading pa[-1] value.
}
}
Despite the fact that after this dereference we are exiting out of loop
and never use p, such behaviour is undefined and should be avoided.
Fix this by moving pointer derference to the beggining of the loop, right
before we will use it.
Signed-off-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
Reviewed-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Alexey Preobrazhensky <preobr@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/idr.c | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)
diff -puN lib/idr.c~lib-idr-fix-out-of-bounds-pointer-dereference lib/idr.c
--- a/lib/idr.c~lib-idr-fix-out-of-bounds-pointer-dereference
+++ a/lib/idr.c
@@ -590,26 +590,27 @@ static void __idr_remove_all(struct idr
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
- p = idp->top;
+ *paa = idp->top;
RCU_INIT_POINTER(idp->top, NULL);
max = idr_max(idp->layers);
id = 0;
while (id >= 0 && id <= max) {
+ p = *paa;
while (n > IDR_BITS && p) {
n -= IDR_BITS;
- *paa++ = p;
p = p->ary[(id >> n) & IDR_MASK];
+ *++paa = p;
}
bt_mask = id;
id += 1 << n;
/* Get the highest bit that the above add changed from 0->1. */
while (n < fls(id ^ bt_mask)) {
- if (p)
- free_layer(idp, p);
+ if (*paa)
+ free_layer(idp, *paa);
n += IDR_BITS;
- p = *--paa;
+ --paa;
}
}
idp->layers = 0;
@@ -692,15 +693,16 @@ int idr_for_each(struct idr *idp,
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
- p = rcu_dereference_raw(idp->top);
+ *paa = rcu_dereference_raw(idp->top);
max = idr_max(idp->layers);
id = 0;
while (id >= 0 && id <= max) {
+ p = *paa;
while (n > 0 && p) {
n -= IDR_BITS;
- *paa++ = p;
p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
+ *++paa = p;
}
if (p) {
@@ -712,7 +714,7 @@ int idr_for_each(struct idr *idp,
id += 1 << n;
while (n < fls(id)) {
n += IDR_BITS;
- p = *--paa;
+ --paa;
}
}
@@ -740,17 +742,18 @@ void *idr_get_next(struct idr *idp, int
int n, max;
/* find first ent */
- p = rcu_dereference_raw(idp->top);
+ p = *paa = rcu_dereference_raw(idp->top);
if (!p)
return NULL;
n = (p->layer + 1) * IDR_BITS;
max = idr_max(p->layer + 1);
while (id >= 0 && id <= max) {
+ p = *paa;
while (n > 0 && p) {
n -= IDR_BITS;
- *paa++ = p;
p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
+ *++paa = p;
}
if (p) {
@@ -768,7 +771,7 @@ void *idr_get_next(struct idr *idp, int
id = round_up(id + 1, 1 << n);
while (n < fls(id)) {
n += IDR_BITS;
- p = *--paa;
+ --paa;
}
}
return NULL;
_
Patches currently in -mm which might be from a.ryabinin@xxxxxxxxxxx are
mm-slabh-wrap-the-whole-file-with-guarding-macro.patch
mm-slub-slub_debug=n-use-the-same-alloc-free-hooks-as-for-slub_debug=y.patch
lib-idr-fix-out-of-bounds-pointer-dereference.patch
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