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author | Simo Sorce <simo@redhat.com> | 2012-12-11 17:23:19 -0500 |
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committer | Jakub Hrozek <jhrozek@redhat.com> | 2012-12-13 20:43:12 +0100 |
commit | a5ccff776edfa776b8846f62a161aaf358e17b66 (patch) | |
tree | 850fbb5199323c380b4ef313c7432c6f5842c826 /src | |
parent | 3cf417b8502f5af34e6680f12a3365bcdd9fa40d (diff) | |
download | sssd-a5ccff776edfa776b8846f62a161aaf358e17b66.tar.gz sssd-a5ccff776edfa776b8846f62a161aaf358e17b66.tar.bz2 sssd-a5ccff776edfa776b8846f62a161aaf358e17b66.zip |
Add a macro to copy with barriers
We have 2 places where we memcpy memory and need barriers protection.
Use a macro so we can consolidate code in one place.
Second fix for: https://fedorahosted.org/sssd/ticket/1694
Diffstat (limited to 'src')
-rw-r--r-- | src/sss_client/nss_mc_common.c | 47 |
1 files changed, 30 insertions, 17 deletions
diff --git a/src/sss_client/nss_mc_common.c b/src/sss_client/nss_mc_common.c index a361f57b..59f5b257 100644 --- a/src/sss_client/nss_mc_common.c +++ b/src/sss_client/nss_mc_common.c @@ -38,18 +38,33 @@ /* FIXME: handle name upper/lower casing ? Maybe a flag passed down by * sssd or a flag in sss_mc_header ? per domain ? */ +#define MEMCPY_WITH_BARRIERS(res, dest, src, len) \ +do { \ + uint32_t _b1; \ + res = false; \ + _b1 = (src)->b1; \ + if (MC_VALID_BARRIER(_b1)) { \ + __sync_synchronize(); \ + memcpy(dest, src, len); \ + __sync_synchronize(); \ + if ((src)->b2 == _b1) { \ + res = true; \ + } \ + } \ +} while(0) + errno_t sss_nss_check_header(struct sss_cli_mc_ctx *ctx) { struct sss_mc_header h; + bool copy_ok; int count; /* retry barrier protected reading max 5 times then give up */ for (count = 5; count > 0; count--) { - memcpy(&h, ctx->mmap_base, sizeof(struct sss_mc_header)); - /* we need a barrier here to make sure the compiler does not optimize - * too much and avoids updating the register for the next check */ - __sync_synchronize(); - if (MC_VALID_BARRIER(h.b1) && h.b1 == h.b2) { + MEMCPY_WITH_BARRIERS(copy_ok, &h, + (struct sss_mc_header *)ctx->mmap_base, + sizeof(struct sss_mc_header)); + if (copy_ok) { /* record is consistent so we can proceed */ break; } @@ -181,11 +196,12 @@ errno_t sss_nss_mc_get_record(struct sss_cli_mc_ctx *ctx, uint32_t slot, struct sss_mc_rec **_rec) { struct sss_mc_rec *rec; - void *rec_buf = NULL; + struct sss_mc_rec *copy_rec = NULL; size_t buf_size = 0; size_t rec_len; uint32_t b1; uint32_t b2; + bool copy_ok; int count; int ret; @@ -198,16 +214,16 @@ errno_t sss_nss_mc_get_record(struct sss_cli_mc_ctx *ctx, __sync_synchronize(); rec_len = rec->len; __sync_synchronize(); - b2 = rec->b1; + b2 = rec->b2; if (!MC_VALID_BARRIER(b1) || b1 != b2) { /* record is inconsistent, retry */ continue; } if (rec_len > buf_size) { - free(rec_buf); - rec_buf = malloc(rec_len); - if (!rec_buf) { + free(copy_rec); + copy_rec = malloc(rec_len); + if (!copy_rec) { ret = ENOMEM; goto done; } @@ -215,13 +231,10 @@ errno_t sss_nss_mc_get_record(struct sss_cli_mc_ctx *ctx, } /* we cannot access data directly, we must copy data and then * access the copy */ - memcpy(rec_buf, rec, rec_len); - rec = (struct sss_mc_rec *)rec_buf; + MEMCPY_WITH_BARRIERS(copy_ok, copy_rec, rec, rec_len); /* we must check data is consistent again after the copy */ - if (MC_VALID_BARRIER(rec->b1) && - rec->b1 == rec->b2 && - rec->len == rec_len) { + if (copy_ok && b1 == copy_rec->b2) { /* record is consistent, use it */ break; } @@ -232,12 +245,12 @@ errno_t sss_nss_mc_get_record(struct sss_cli_mc_ctx *ctx, goto done; } - *_rec = rec; + *_rec = copy_rec; ret = 0; done: if (ret) { - free(rec_buf); + free(copy_rec); *_rec = NULL; } return ret; |