Messages in this thread Patch in this message | | | Subject | [PATCH] Fix hashing in 2.4.0 rpcauth code (was Re: bug in rpc code) | From | Trond Myklebust <> | Date | 13 Oct 2000 11:25:40 +0200 |
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>>>>> " " == Hai-Pao Fan <haipao@mvista.com> writes:
> Problem:
> A returned address from kmalloc() can be overwritten to a wrong > place in rpcauth_lookup_credcache() routine.
Ouch. This is a bug that's been with us since 2.1.x at least...
Linus, the problem is in fact twofold.
1) auth_null is not initializing cred->cr_uid as it is required to do by the rpc_auth hashing scheme. The latter should really have be rewritten: we don't actually need hashing for auth_null, since there is nothing uid-specific in the credential. (Appended to the TODO list for 2.5)
2) The hashing scheme itself uses the 'mod' a.k.a. '%' operation on signed quantities. This means that offsets into the hash table can turn negative...
The following patch should clear it up on 2.4.0. I'll send a separate patch to Alan for inclusion into 2.2.18.
Cheers, Trond
--- net/sunrpc/auth_null.c.orig Mon Mar 20 17:14:04 2000 +++ net/sunrpc/auth_null.c Fri Oct 13 09:44:02 2000 @@ -54,6 +54,7 @@ return NULL; cred->cr_count = 0; cred->cr_flags = RPCAUTH_CRED_UPTODATE; + cred->cr_uid = current->uid; return cred; } --- net/sunrpc/auth.c.orig Sat May 13 18:43:55 2000 +++ net/sunrpc/auth.c Fri Oct 13 10:36:54 2000 @@ -159,7 +159,7 @@ { int nr; - nr = (cred->cr_uid % RPC_CREDCACHE_NR); + nr = (cred->cr_uid & RPC_CREDCACHE_MASK); spin_lock(&rpc_credcache_lock); cred->cr_next = auth->au_credcache[nr]; auth->au_credcache[nr] = cred; @@ -178,7 +178,7 @@ int nr = 0; if (!(taskflags & RPC_TASK_ROOTCREDS)) - nr = current->uid % RPC_CREDCACHE_NR; + nr = current->uid & RPC_CREDCACHE_MASK; if (time_before(auth->au_nextgc, jiffies)) rpcauth_gc_credcache(auth); @@ -218,7 +218,7 @@ struct rpc_cred **q, *cr; int nr; - nr = (cred->cr_uid % RPC_CREDCACHE_NR); + nr = (cred->cr_uid & RPC_CREDCACHE_MASK); spin_lock(&rpc_credcache_lock); q = &auth->au_credcache[nr]; while ((cr = *q) != NULL) { --- include/linux/sunrpc/auth.h.orig Fri Oct 13 10:06:19 2000 +++ include/linux/sunrpc/auth.h Fri Oct 13 10:35:42 2000 @@ -43,6 +43,7 @@ * Client authentication handle */ #define RPC_CREDCACHE_NR 8 +#define RPC_CREDCACHE_MASK (RPC_CREDCACHE_NR - 1) struct rpc_auth { struct rpc_cred * au_credcache[RPC_CREDCACHE_NR]; unsigned long au_expire; /* cache expiry interval */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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