2012-02-16 16:58:31

by Xi Wang

Subject: [PATCH] libceph: fix overflow check in crush_decode()

The existing overflow check (n > ULONG_MAX / b) didn't work, because
n = ULONG_MAX / b would both bypass the check and still overflow the
allocation size a + n * b.

The correct check should be (n > (ULONG_MAX - a) / b).

Signed-off-by: Xi Wang <[email protected]>
---
net/ceph/osdmap.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
index fd863fe..29ad46e 100644
--- a/net/ceph/osdmap.c
+++ b/net/ceph/osdmap.c
@@ -283,7 +283,8 @@ static struct crush_map *crush_decode(void *pbyval, void *end)
ceph_decode_32_safe(p, end, yes, bad);
#if BITS_PER_LONG == 32
err = -EINVAL;
- if (yes > ULONG_MAX / sizeof(struct crush_rule_step))
+ if (yes > (ULONG_MAX - sizeof(*r))
+ / sizeof(struct crush_rule_step))
goto bad;
#endif
r = c->rules[i] = kmalloc(sizeof(*r) +
--
1.7.5.4

2012-02-16 17:55:28

by Sage Weil

Subject: Re: [PATCH] libceph: fix overflow check in crush_decode()

Applied these both, thanks!

sage

On Thu, 16 Feb 2012, Xi Wang wrote:

> The existing overflow check (n > ULONG_MAX / b) didn't work, because
> n = ULONG_MAX / b would both bypass the check and still overflow the
> allocation size a + n * b.
>
> The correct check should be (n > (ULONG_MAX - a) / b).
>
> Signed-off-by: Xi Wang <[email protected]>
> ---
> net/ceph/osdmap.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
> index fd863fe..29ad46e 100644
> --- a/net/ceph/osdmap.c
> +++ b/net/ceph/osdmap.c
> @@ -283,7 +283,8 @@ static struct crush_map *crush_decode(void *pbyval, void *end)
> ceph_decode_32_safe(p, end, yes, bad);
> #if BITS_PER_LONG == 32
> err = -EINVAL;
> - if (yes > ULONG_MAX / sizeof(struct crush_rule_step))
> + if (yes > (ULONG_MAX - sizeof(*r))
> + / sizeof(struct crush_rule_step))
> goto bad;
> #endif
> r = c->rules[i] = kmalloc(sizeof(*r) +
> --
> 1.7.5.4
>
> --
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