On 11.11.2024 22:04, Jeongjun Park wrote:
Manas <devnull+manas18244.iiitd.ac.in@xxxxxxxxxx> wrote:
The last parameter in __smc_diag_dump (struct nlattr *bc) is unused.
There is only one instance of this function being called and its passed
with a NULL value in place of bc.
Signed-off-by: Manas <manas18244@xxxxxxxxxxx>
---
The last parameter in __smc_diag_dump (struct nlattr *bc) is unused.
There is only one instance of this function being called and its passed
with a NULL value in place of bc.
Though, the compiler (gcc) optimizes it. Looking at the object dump of
vmlinux (via `objdump -D vmlinux`), a new function clone
(__smc_diag_dump.constprop.0) is added which removes this parameter from
calling convention altogether.
ffffffff8a701770 <__smc_diag_dump.constprop.0>:
ffffffff8a701770: 41 57 push %r15
ffffffff8a701772: 41 56 push %r14
ffffffff8a701774: 41 55 push %r13
ffffffff8a701776: 41 54 push %r12
There are 5 parameters in original function, but in the cloned function
only 4.
I believe this patch also fixes this oops bug[1], which arises in the
same function __smc_diag_dump. But I couldn't verify it further. Can
someone please test this?
[1] https://syzkaller.appspot.com/bug?extid=271fed3ed6f24600c364
Unfortunately, I tested it myself and this bug is still triggering. Basically,
this bug is not triggered in normal situations, but triggered when a race
condition occurs, so I think the root cause is somewhere else.
Thank you Jeongjun for reviewing this.
---
net/smc/smc_diag.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/net/smc/smc_diag.c b/net/smc/smc_diag.c
index 6fdb2d96777ad704c394709ec845f9ddef5e599a..8f7bd40f475945171a0afa5a2cce12d9aa2b1eb4 100644
--- a/net/smc/smc_diag.c
+++ b/net/smc/smc_diag.c
@@ -71,8 +71,7 @@ static int smc_diag_msg_attrs_fill(struct sock *sk, struct sk_buff *skb,
static int __smc_diag_dump(struct sock *sk, struct sk_buff *skb,
struct netlink_callback *cb,
- const struct smc_diag_req *req,
- struct nlattr *bc)
+ const struct smc_diag_req *req)
{
struct smc_sock *smc = smc_sk(sk);
struct smc_diag_fallback fallback;
@@ -199,7 +198,6 @@ static int smc_diag_dump_proto(struct proto *prot, struct sk_buff *skb,
struct smc_diag_dump_ctx *cb_ctx = smc_dump_context(cb);
struct net *net = sock_net(skb->sk);
int snum = cb_ctx->pos[p_type];
- struct nlattr *bc = NULL;
struct hlist_head *head;
int rc = 0, num = 0;
struct sock *sk;
@@ -214,7 +212,7 @@ static int smc_diag_dump_proto(struct proto *prot, struct sk_buff *skb,
continue;
if (num < snum)
goto next;
- rc = __smc_diag_dump(sk, skb, cb, nlmsg_data(cb->nlh), bc);
+ rc = __smc_diag_dump(sk, skb, cb, nlmsg_data(cb->nlh));
if (rc < 0)
goto out;
next:
---
base-commit: 59b723cd2adbac2a34fc8e12c74ae26ae45bf230
change-id: 20241109-fix-oops-__smc_diag_dump-06ab3e9d39f4
Best regards,
--
Manas <manas18244@xxxxxxxxxxx>
--
Manas
