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 571ed1fd2390 ("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@xxxxxxxx> Fixes: 571ed1fd2390 ("SUNRPC: Replace krb5_seq_lock with a lockless scheme") Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> Cc: Anna Schumaker <anna.schumaker@xxxxxxxxxx> Cc: J. Bruce Fields <bfields@xxxxxxxxxxxx> Cc: Jeff Layton <jlayton@xxxxxxxxxx> Cc: David S. Miller <davem@xxxxxxxxxxxxx> Cc: linux-nfs@xxxxxxxxxxxxxxx Cc: netdev@xxxxxxxxxxxxxxx --- include/linux/sunrpc/gss_krb5.h | 7 ++----- net/sunrpc/auth_gss/gss_krb5_mech.c | 16 ++++++++++------ net/sunrpc/auth_gss/gss_krb5_seal.c | 28 ++-------------------------- net/sunrpc/auth_gss/gss_krb5_wrap.c | 4 ++-- 4 files changed, 16 insertions(+), 39 deletions(-) diff --git a/include/linux/sunrpc/gss_krb5.h b/include/linux/sunrpc/gss_krb5.h index 131424cefc6a..02c0412e368c 100644 --- a/include/linux/sunrpc/gss_krb5.h +++ b/include/linux/sunrpc/gss_krb5.h @@ -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) diff --git a/net/sunrpc/auth_gss/gss_krb5_mech.c b/net/sunrpc/auth_gss/gss_krb5_mech.c index 7f0424dfa8f6..eab71fc7af3e 100644 --- a/net/sunrpc/auth_gss/gss_krb5_mech.c +++ b/net/sunrpc/auth_gss/gss_krb5_mech.c @@ -274,6 +274,7 @@ get_key(const void *p, const void *end, 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)); @@ -315,9 +316,10 @@ 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; @@ -607,6 +609,7 @@ 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)); @@ -617,14 +620,15 @@ 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; } diff --git a/net/sunrpc/auth_gss/gss_krb5_seal.c b/net/sunrpc/auth_gss/gss_krb5_seal.c index b4adeb06660b..48fe4a591b54 100644 --- a/net/sunrpc/auth_gss/gss_krb5_seal.c +++ b/net/sunrpc/auth_gss/gss_krb5_seal.c @@ -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) { diff --git a/net/sunrpc/auth_gss/gss_krb5_wrap.c b/net/sunrpc/auth_gss/gss_krb5_wrap.c index 962fa84e6db1..5cdde6cb703a 100644 --- a/net/sunrpc/auth_gss/gss_krb5_wrap.c +++ b/net/sunrpc/auth_gss/gss_krb5_wrap.c @@ -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) -- 2.19.1