The commit is pushed to "branch-rh7-3.10.0-229.7.2-ovz" and will appear at
https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-229.7.2.vz7.6.6
------>
commit fd0dd7792b2302e1d811fee88208faebbdb8ffe2
Author: Andrey Ryabinin <[email protected]>
Date: Thu Sep 3 19:27:31 2015 +0400
ms/lib/idr.c: fix out-of-bounds pointer dereference
https://jira.sw.ru/browse/PSBM-26429
From: Andrey Ryabinin <[email protected]>
commit 93b7aca35dd7bf0c3ba7ea0542b556bcfdb28e76 upstream.
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 <[email protected]>
Reviewed-by: Lai Jiangshan <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Alexey Preobrazhensky <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Andrey Ryabinin <[email protected]>
Signed-off-by: Andrey Ryabinin <[email protected]>
---
lib/idr.c | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/lib/idr.c b/lib/idr.c
index 674c30b..0859b3a 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -616,26 +616,27 @@ void __idr_remove_all(struct idr *idp)
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
- p = idp->top;
+ *paa = idp->top;
rcu_assign_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;
@@ -719,15 +720,16 @@ 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) {
@@ -739,7 +741,7 @@ int idr_for_each(struct idr *idp,
id += 1 << n;
while (n < fls(id)) {
n += IDR_BITS;
- p = *--paa;
+ --paa;
}
}
@@ -767,17 +769,18 @@ void *idr_get_next(struct idr *idp, int *nextidp)
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) {
@@ -795,7 +798,7 @@ void *idr_get_next(struct idr *idp, int *nextidp)
id = round_up(id + 1, 1 << n);
while (n < fls(id)) {
n += IDR_BITS;
- p = *--paa;
+ --paa;
}
}
return NULL;
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