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SUNRPC: Use atomic(64)_t for seq_send(64) 

The seq_send & seq_send64 fields in struct krb5_ctx are used as
atomically incrementing counters. This is implemented using cmpxchg() &
cmpxchg64() to implement what amount to custom versions of
atomic_fetch_inc() & atomic64_fetch_inc().

Besides the duplication, using cmpxchg64() has another major drawback in
that some 32 bit architectures don't provide it. As such commit
571ed1fd23 ("SUNRPC: Replace krb5_seq_lock with a lockless scheme")
resulted in build failures for some architectures.

Change seq_send to be an atomic_t and seq_send64 to be an atomic64_t,
then use atomic(64)_* functions to manipulate the values. The atomic64_t
type & associated functions are provided even on architectures which
lack real 64 bit atomic memory access via CONFIG_GENERIC_ATOMIC64 which
uses spinlocks to serialize access. This fixes the build failures for
architectures lacking cmpxchg64().

A potential alternative that was raised would be to provide cmpxchg64()
on the 32 bit architectures that currently lack it, using spinlocks.
However this would provide a version of cmpxchg64() with semantics a
little different to the implementations on architectures with real 64
bit atomics - the spinlock-based implementation would only work if all
access to the memory used with cmpxchg64() is *always* performed using
cmpxchg64(). That is not currently a requirement for users of
cmpxchg64(), and making it one seems questionable. As such avoiding
cmpxchg64() outside of architecture-specific code seems best,
particularly in cases where atomic64_t seems like a better fit anyway.

The CONFIG_GENERIC_ATOMIC64 implementation of atomic64_* functions will
use spinlocks & so faces the same issue, but with the key difference
that the memory backing an atomic64_t ought to always be accessed via
the atomic64_* functions anyway making the issue moot.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: 571ed1fd23 ("SUNRPC: Replace krb5_seq_lock with a lockless scheme")
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: J. Bruce Fields <bfields@fieldses.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: linux-nfs@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Paul Burton 2018-11-01 17:51:34 +00:00 committed by Trond Myklebust
parent 86bbd7422a
commit c3be6577d8
4 changed files with 16 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/sunrpc/gss_krb5.h
View File

@ -107,8 +107,8 @@ struct krb5_ctx {
u8 Ksess[GSS_KRB5_MAX_KEYLEN]; /* session key */
u8 cksum[GSS_KRB5_MAX_KEYLEN];
s32 endtime;
u32 seq_send;
u64 seq_send64;
atomic_t seq_send;
atomic64_t seq_send64;
struct xdr_netobj mech_used;
u8 initiator_sign[GSS_KRB5_MAX_KEYLEN];
u8 acceptor_sign[GSS_KRB5_MAX_KEYLEN];
@ -118,9 +118,6 @@ struct krb5_ctx {
u8 acceptor_integ[GSS_KRB5_MAX_KEYLEN];
};
extern u32 gss_seq_send_fetch_and_inc(struct krb5_ctx *ctx);
extern u64 gss_seq_send64_fetch_and_inc(struct krb5_ctx *ctx);
/* The length of the Kerberos GSS token header */
#define GSS_KRB5_TOK_HDR_LEN (16)

16
net/sunrpc/auth_gss/gss_krb5_mech.c
View File

@ -275,6 +275,7 @@ out_err:
static int
gss_import_v1_context(const void *p, const void *end, struct krb5_ctx *ctx)
{
u32 seq_send;
int tmp;
p = simple_get_bytes(p, end, &ctx->initiate, sizeof(ctx->initiate));
@ -316,9 +317,10 @@ gss_import_v1_context(const void *p, const void *end, struct krb5_ctx *ctx)
p = simple_get_bytes(p, end, &ctx->endtime, sizeof(ctx->endtime));
if (IS_ERR(p))
goto out_err;
p = simple_get_bytes(p, end, &ctx->seq_send, sizeof(ctx->seq_send));
p = simple_get_bytes(p, end, &seq_send, sizeof(seq_send));
if (IS_ERR(p))
goto out_err;
atomic_set(&ctx->seq_send, seq_send);
p = simple_get_netobj(p, end, &ctx->mech_used);
if (IS_ERR(p))
goto out_err;
@ -610,6 +612,7 @@ static int
gss_import_v2_context(const void *p, const void *end, struct krb5_ctx *ctx,
gfp_t gfp_mask)
{
u64 seq_send64;
int keylen;
p = simple_get_bytes(p, end, &ctx->flags, sizeof(ctx->flags));
@ -620,14 +623,15 @@ gss_import_v2_context(const void *p, const void *end, struct krb5_ctx *ctx,
p = simple_get_bytes(p, end, &ctx->endtime, sizeof(ctx->endtime));
if (IS_ERR(p))
goto out_err;
p = simple_get_bytes(p, end, &ctx->seq_send64, sizeof(ctx->seq_send64));
p = simple_get_bytes(p, end, &seq_send64, sizeof(seq_send64));
if (IS_ERR(p))
goto out_err;
atomic64_set(&ctx->seq_send64, seq_send64);
/* set seq_send for use by "older" enctypes */
ctx->seq_send = ctx->seq_send64;
if (ctx->seq_send64 != ctx->seq_send) {
dprintk("%s: seq_send64 %lx, seq_send %x overflow?\n", __func__,
(unsigned long)ctx->seq_send64, ctx->seq_send);
atomic_set(&ctx->seq_send, seq_send64);
if (seq_send64 != atomic_read(&ctx->seq_send)) {
dprintk("%s: seq_send64 %llx, seq_send %x overflow?\n", __func__,
seq_send64, atomic_read(&ctx->seq_send));
p = ERR_PTR(-EINVAL);
goto out_err;
}

28
net/sunrpc/auth_gss/gss_krb5_seal.c
View File

@ -123,30 +123,6 @@ setup_token_v2(struct krb5_ctx *ctx, struct xdr_netobj *token)
return krb5_hdr;
}
u32
gss_seq_send_fetch_and_inc(struct krb5_ctx *ctx)
{
u32 old, seq_send = READ_ONCE(ctx->seq_send);
do {
old = seq_send;
seq_send = cmpxchg(&ctx->seq_send, old, old + 1);
} while (old != seq_send);
return seq_send;
}
u64
gss_seq_send64_fetch_and_inc(struct krb5_ctx *ctx)
{
u64 old, seq_send = READ_ONCE(ctx->seq_send);
do {
old = seq_send;
seq_send = cmpxchg64(&ctx->seq_send64, old, old + 1);
} while (old != seq_send);
return seq_send;
}
static u32
gss_get_mic_v1(struct krb5_ctx *ctx, struct xdr_buf *text,
struct xdr_netobj *token)
@ -177,7 +153,7 @@ gss_get_mic_v1(struct krb5_ctx *ctx, struct xdr_buf *text,
memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data, md5cksum.len);
seq_send = gss_seq_send_fetch_and_inc(ctx);
seq_send = atomic_fetch_inc(&ctx->seq_send);
if (krb5_make_seq_num(ctx, ctx->seq, ctx->initiate ? 0 : 0xff,
seq_send, ptr + GSS_KRB5_TOK_HDR_LEN, ptr + 8))
@ -205,7 +181,7 @@ gss_get_mic_v2(struct krb5_ctx *ctx, struct xdr_buf *text,
/* Set up the sequence number. Now 64-bits in clear
* text and w/o direction indicator */
seq_send_be64 = cpu_to_be64(gss_seq_send64_fetch_and_inc(ctx));
seq_send_be64 = cpu_to_be64(atomic64_fetch_inc(&ctx->seq_send64));
memcpy(krb5_hdr + 8, (char *) &seq_send_be64, 8);
if (ctx->initiate) {

4
net/sunrpc/auth_gss/gss_krb5_wrap.c
View File

@ -228,7 +228,7 @@ gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data, md5cksum.len);
seq_send = gss_seq_send_fetch_and_inc(kctx);
seq_send = atomic_fetch_inc(&kctx->seq_send);
/* XXX would probably be more efficient to compute checksum
* and encrypt at the same time: */
@ -475,7 +475,7 @@ gss_wrap_kerberos_v2(struct krb5_ctx *kctx, u32 offset,
*be16ptr++ = 0;
be64ptr = (__be64 *)be16ptr;
*be64ptr = cpu_to_be64(gss_seq_send64_fetch_and_inc(kctx));
*be64ptr = cpu_to_be64(atomic64_fetch_inc(&kctx->seq_send64));
err = (*kctx->gk5e->encrypt_v2)(kctx, offset, buf, pages);
if (err)