[PATCH v2] infiniband/uverbs: Fix integer overflows

Vlad Tsyrklevich
2017-03-24T19:55:17Z

The 'num_sge' variable is verfied to be smaller than the 'sge_count'
variable; however, since both are user-controlled it's possible to cause
an integer overflow for the kmalloc multiply on 32-bit platforms
(num_sge and sge_count are both defined u32). By crafting an input that
causes a smaller-than-expected allocation it's possible to write
controlled data out-of-bounds.

Signed-off-by: Vlad Tsyrklevich <vlad-NIZqynvkaCU43zv7NVfAiQ@public.gmane.org>
---
drivers/infiniband/core/uverbs_cmd.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 7007822..5469088 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -2542,9 +2542,13 @@ ssize_t ib_uverbs_destroy_qp(struct ib_uverbs_file *file,

static void *alloc_wr(size_t wr_size, __u32 num_sge)
{
+ if (num_sge >= (U32_MAX - ALIGN(wr_size, sizeof (struct ib_sge))) /
+ sizeof (struct ib_sge))
+ return NULL;
+
return kmalloc(ALIGN(wr_size, sizeof (struct ib_sge)) +
num_sge * sizeof (struct ib_sge), GFP_KERNEL);
-};
+}

ssize_t ib_uverbs_post_send(struct ib_uverbs_file *file,
struct ib_device *ib_dev,
@@ -2771,6 +2775,13 @@ static struct ib_recv_wr *ib_uverbs_unmarshall_recv(const char __user *buf,
goto err;
}

+ if (user_wr->num_sge >=
+ (U32_MAX - ALIGN(sizeof *next, sizeof (struct ib_sge))) /
+ sizeof (struct ib_sge)) {
+ ret = -EINVAL;
+ goto err;
+ }
+
next = kmalloc(ALIGN(sizeof *next, sizeof (struct ib_sge)) +
user_wr->num_sge * sizeof (struct ib_sge),
GFP_KERNEL);
--
2.7.0