Re: [PATCH net] rxrpc: Truncate UTS_RELEASE for rxrpc version

[Jeffrey E Altman]

On 5/26/2023 7:34 AM, David Howells wrote:
> UTS_RELEASE has a maximum length of 64 which can cause rxrpc_version to
> exceed the 65 byte message limit.
>
> Per the rx spec[1]: "If a server receives a packet with a type value 
> of 13,
> and the client-initiated flag set, it should respond with a 65-byte 
> payload
> containing a string that identifies the version of AFS software it is
> running."
>
> The current implementation causes a compile error when WERROR is turned on
> and/or UTS_RELEASE exceeds the length of 49 (making the version string 
> more
> than 64 characters).
>
> Fix this by generating the string during module initialisation and 
> limiting
> the UTS_RELEASE segment of the string does not exceed 49 chars. We need to
> make sure that the 64 bytes includes "linux-" at the front and " AF_RXRPC"
> at the back as this may be used in pattern matching.
>
> Fixes: 44ba06987c0b ("RxRPC: Handle VERSION Rx protocol packets")
> Reported-by: Kenny Ho <Kenny.Ho@xxxxxxx>
> Link: https://lore.kernel.org/r/20230523223944.691076-1-Kenny.Ho@xxxxxxx/
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> Acked-by: Kenny Ho <Kenny.Ho@xxxxxxx>
> cc: Marc Dionne <marc.dionne@xxxxxxxxxxxx>
> cc: Andrew Lunn <andrew@xxxxxxx>
> cc: David Laight <David.Laight@xxxxxxxxxx>
> cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> cc: linux-afs@xxxxxxxxxxxxxxxxxxx
> cc: netdev@xxxxxxxxxxxxxxx
> Link: https://web.mit.edu/kolya/afs/rx/rx-spec [1]
> ---
> net/rxrpc/af_rxrpc.c | 1 +
> net/rxrpc/ar-internal.h | 1 +
> net/rxrpc/local_event.c | 11 ++++++++++-
> 3 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c
> index 31f738d65f1c..da0b3b5157d5 100644
> --- a/net/rxrpc/af_rxrpc.c
> +++ b/net/rxrpc/af_rxrpc.c
> @@ -980,6 +980,7 @@ static int __init af_rxrpc_init(void)
> BUILD_BUG_ON(sizeof(struct rxrpc_skb_priv) > sizeof_field(struct 
> sk_buff, cb));
> ret = -ENOMEM;
> + rxrpc_gen_version_string();
> rxrpc_call_jar = kmem_cache_create(
> "rxrpc_call_jar", sizeof(struct rxrpc_call), 0,
> SLAB_HWCACHE_ALIGN, NULL);
> diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
> index 5d44dc08f66d..e8e14c6f904d 100644
> --- a/net/rxrpc/ar-internal.h
> +++ b/net/rxrpc/ar-internal.h
> @@ -1068,6 +1068,7 @@ int rxrpc_get_server_data_key(struct 
> rxrpc_connection *, const void *, time64_t,
> /*
> * local_event.c
> */
> +void rxrpc_gen_version_string(void);
> void rxrpc_send_version_request(struct rxrpc_local *local,
> struct rxrpc_host_header *hdr,
> struct sk_buff *skb);
> diff --git a/net/rxrpc/local_event.c b/net/rxrpc/local_event.c
> index 5e69ea6b233d..993c69f97488 100644
> --- a/net/rxrpc/local_event.c
> +++ b/net/rxrpc/local_event.c
> @@ -16,7 +16,16 @@
> #include <generated/utsrelease.h>
> #include "ar-internal.h"
> -static const char rxrpc_version_string[65] = "linux-" UTS_RELEASE " 
> AF_RXRPC";
> +static char rxrpc_version_string[65]; // "linux-" UTS_RELEASE " 
> AF_RXRPC";
> +
> +/*
> + * Generate the VERSION packet string.
> + */
> +void rxrpc_gen_version_string(void)
> +{
> + snprintf(rxrpc_version_string, sizeof(rxrpc_version_string),
> + "linux-%.49s AF_RXRPC", UTS_RELEASE);
> +}
> /*
> * Reply to a version request
Reviewed-by: Jeffrey Altman <jaltman@xxxxxxxxxxxx>

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