Dynamically allocate the NLM host structure in order to avoid stack overflow.
nlmsvc_mark_resources() is several call levels deep in a stack
that has a number of large variables. 512 bytes seems like a lot
on the stack at this point.
smatch analysis:
fs/lockd/svcsubs.c:366 nlmsvc_mark_resources() warn: 'hint' puts
512 bytes on stack
Cc: Trond Myklebust <[email protected]>
Cc: "J. Bruce Fields" <[email protected]>
Cc: [email protected]
Signed-off-by: Tim Gardner <[email protected]>
---
fs/lockd/svcsubs.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c
index b904f41..f3abb7f 100644
--- a/fs/lockd/svcsubs.c
+++ b/fs/lockd/svcsubs.c
@@ -363,11 +363,15 @@ nlmsvc_is_client(void *data, struct nlm_host *dummy)
void
nlmsvc_mark_resources(struct net *net)
{
- struct nlm_host hint;
+ struct nlm_host *hint = kzalloc(sizeof(*hint), GFP_KERNEL);
- dprintk("lockd: nlmsvc_mark_resources for net %p\n", net);
- hint.net = net;
- nlm_traverse_files(&hint, nlmsvc_mark_host, NULL);
+ if (hint) {
+ dprintk("lockd: nlmsvc_mark_resources for net %p\n", net);
+ hint->net = net;
+ nlm_traverse_files(hint, nlmsvc_mark_host, NULL);
+ }
+
+ kfree(hint);
}
/*
--
1.7.9.5
On 02/12/2013 02:22 PM, J. Bruce Fields wrote:
> On Tue, Feb 12, 2013 at 12:48:58PM -0700, Tim Gardner wrote:
>> Dynamically allocate the NLM host structure in order to avoid stack overflow.
>> nlmsvc_mark_resources() is several call levels deep in a stack
>> that has a number of large variables. 512 bytes seems like a lot
>> on the stack at this point.
>>
>> smatch analysis:
>>
>> fs/lockd/svcsubs.c:366 nlmsvc_mark_resources() warn: 'hint' puts
>> 512 bytes on stack
>>
>> Cc: Trond Myklebust <[email protected]>
>> Cc: "J. Bruce Fields" <[email protected]>
>> Cc: [email protected]
>> Signed-off-by: Tim Gardner <[email protected]>
>> ---
>> fs/lockd/svcsubs.c | 12 ++++++++----
>> 1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c
>> index b904f41..f3abb7f 100644
>> --- a/fs/lockd/svcsubs.c
>> +++ b/fs/lockd/svcsubs.c
>> @@ -363,11 +363,15 @@ nlmsvc_is_client(void *data, struct nlm_host *dummy)
>> void
>> nlmsvc_mark_resources(struct net *net)
>> {
>> - struct nlm_host hint;
>> + struct nlm_host *hint = kzalloc(sizeof(*hint), GFP_KERNEL);
>>
>> - dprintk("lockd: nlmsvc_mark_resources for net %p\n", net);
>> - hint.net = net;
>> - nlm_traverse_files(&hint, nlmsvc_mark_host, NULL);
>> + if (hint) {
>> + dprintk("lockd: nlmsvc_mark_resources for net %p\n", net);
>> + hint->net = net;
>> + nlm_traverse_files(hint, nlmsvc_mark_host, NULL);
>> + }
>
> Silently neglecting to do this looks like a bad idea.
>
> It's strange that we're passing in an nlm_host when all we actually use
> is the struct net*. Why not just change this to pass in the net
> instead?
>
> --b.
>
It won't really be silent. k[zm]alloc() dumps a stack trace on failure
to allocate unless GFP_NOWARN is set in the flags. I think this is a bit
better then possibly corrupting the stack.
Changing the prototype to just pass in 'net' has knock on effects that
make this patch a whole lot bigger. You'd have to change the code within
a bunch of functions which are difficult to verify at compile time
because of the use of 'void *data' as the first parameter. Is there
still a good reason for that parameter to be opaque ?
rtg
--
Tim Gardner [email protected]
On Tue, Feb 12, 2013 at 12:48:58PM -0700, Tim Gardner wrote:
> Dynamically allocate the NLM host structure in order to avoid stack overflow.
> nlmsvc_mark_resources() is several call levels deep in a stack
> that has a number of large variables. 512 bytes seems like a lot
> on the stack at this point.
>
> smatch analysis:
>
> fs/lockd/svcsubs.c:366 nlmsvc_mark_resources() warn: 'hint' puts
> 512 bytes on stack
>
> Cc: Trond Myklebust <[email protected]>
> Cc: "J. Bruce Fields" <[email protected]>
> Cc: [email protected]
> Signed-off-by: Tim Gardner <[email protected]>
> ---
> fs/lockd/svcsubs.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c
> index b904f41..f3abb7f 100644
> --- a/fs/lockd/svcsubs.c
> +++ b/fs/lockd/svcsubs.c
> @@ -363,11 +363,15 @@ nlmsvc_is_client(void *data, struct nlm_host *dummy)
> void
> nlmsvc_mark_resources(struct net *net)
> {
> - struct nlm_host hint;
> + struct nlm_host *hint = kzalloc(sizeof(*hint), GFP_KERNEL);
>
> - dprintk("lockd: nlmsvc_mark_resources for net %p\n", net);
> - hint.net = net;
> - nlm_traverse_files(&hint, nlmsvc_mark_host, NULL);
> + if (hint) {
> + dprintk("lockd: nlmsvc_mark_resources for net %p\n", net);
> + hint->net = net;
> + nlm_traverse_files(hint, nlmsvc_mark_host, NULL);
> + }
Silently neglecting to do this looks like a bad idea.
It's strange that we're passing in an nlm_host when all we actually use
is the struct net*. Why not just change this to pass in the net
instead?
--b.
> +
> + kfree(hint);
> }
>
> /*
> --
> 1.7.9.5
>