This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].
As the "ids" variable is a pointer to "struct sctp_assoc_ids" and this
structure ends in a flexible array:
struct sctp_assoc_ids {
[...]
sctp_assoc_t gaids_assoc_id[];
};
the preferred way in the kernel is to use the struct_size() helper to
do the arithmetic instead of the calculation "size + size * count" in
the kmalloc() function.
Also, refactor the code adding the "ids_size" variable to avoid sizing
twice.
This way, the code is more readable and safer.
This code was detected with the help of Coccinelle, and audited and
modified manually.
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Signed-off-by: Erick Archer <erick.archer@xxxxxxxxxxx>
---
Hi,
The Coccinelle script used to detect this code pattern is the following:
virtual report
@rule1@
type t1;
type t2;
identifier i0;
identifier i1;
identifier i2;
identifier ALLOC =~ "kmalloc|kzalloc|kmalloc_node|kzalloc_node|vmalloc|vzalloc|kvmalloc|kvzalloc";
position p1;
@@
i0 = sizeof(t1) + sizeof(t2) * i1;
...
i2 = ALLOC@p1(..., i0, ...);
@script:python depends on report@
p1 << rule1.p1;
@@
msg = "WARNING: verify allocation on line %s" % (p1[0].line)
coccilib.report.print_report(p1[0],msg)
Regards,
Erick
---
net/sctp/socket.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index e416b6d3d270..64196b1dce1d 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -7119,6 +7119,7 @@ static int sctp_getsockopt_assoc_ids(struct sock *sk, int len,
struct sctp_sock *sp = sctp_sk(sk);
struct sctp_association *asoc;
struct sctp_assoc_ids *ids;
+ size_t ids_size;
u32 num = 0;
if (sctp_style(sk, TCP))
@@ -7131,11 +7132,11 @@ static int sctp_getsockopt_assoc_ids(struct sock *sk, int len,
num++;
}
- if (len < sizeof(struct sctp_assoc_ids) + sizeof(sctp_assoc_t) * num)
+ ids_size = struct_size(ids, gaids_assoc_id, num);
+ if (len < ids_size)
return -EINVAL;
- len = sizeof(struct sctp_assoc_ids) + sizeof(sctp_assoc_t) * num;
-
+ len = ids_size;
ids = kmalloc(len, GFP_USER | __GFP_NOWARN);
if (unlikely(!ids))
return -ENOMEM;
--
2.25.1
