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authorAndrey Ryabinin <a.ryabinin@samsung.com>2014-08-08 21:22:07 (GMT)
committerChanho Park <chanho61.park@samsung.com>2015-01-05 04:50:16 (GMT)
commit6bb1b36726e8a9c8232fc2ec70796817b14d8f8e (patch)
tree127f77f92ba4ee456b3031e7ee53ffb51de23dda
parent942d62204e43fa8280f702e4bed9f65aa3cde745 (diff)
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lib/idr.c: fix out-of-bounds pointer dereferencerefs/changes/22/32822/2
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@samsung.com> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Tejun Heo <tj@kernel.org> Cc: Alexey Preobrazhensky <preobr@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Change-Id: Id151fc7e874e3cff64da43eb3359f022de7e6cae Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
-rw-r--r--lib/idr.c25
1 files changed, 14 insertions, 11 deletions
diff --git a/lib/idr.c b/lib/idr.c
index a3bfde8..dd06ccb 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -618,26 +618,27 @@ 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;
@@ -721,15 +722,16 @@ 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) {
@@ -741,7 +743,7 @@ int idr_for_each(struct idr *idp,
id += 1 << n;
while (n < fls(id)) {
n += IDR_BITS;
- p = *--paa;
+ --paa;
}
}
@@ -769,17 +771,18 @@ 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) {
@@ -797,7 +800,7 @@ 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;