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Fix stack dsl_deleg_get()

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Reduce stack usage in dsl_deleg_get, gcc flagged it as consuming a
whopping 1040 bytes or potentially 1/4 of a 4K stack.  This patch
moves all the large structures and buffer off the stack and on to
the heap.  This includes 2 zap_cursor_t structs each 52 bytes in
size, 2 zap_attribute_t structs each 280 bytes in size, and 1
256 byte char array.  The total saves on the stack is 880 bytes
after you account for the 5 new pointers added.

Also the source buffer length has been increased from MAXNAMELEN
to MAXNAMELEN+strlen(MOS_DIR_NAME)+1 as described by the comment in
dsl_dir_name().  A buffer overrun may have been possible with the
slightly smaller buffer.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
This commit is contained in:
Brian Behlendorf 2010-08-26 10:53:19 -07:00
parent 81a4966389
commit 48c67dc8f8
1 changed files with 26 additions and 17 deletions
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43
module/zfs/dsl_deleg.c
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@ -296,6 +296,9 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
dsl_pool_t *dp;
int error;
objset_t *mos;
zap_cursor_t *basezc, *zc;
zap_attribute_t *baseza, *za;
char *source;
error = dsl_dir_open(ddname, FTAG, &startdd, NULL);
if (error)
@ -304,15 +307,17 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
dp = startdd->dd_pool;
mos = dp->dp_meta_objset;
zc = kmem_alloc(sizeof(zap_cursor_t), KM_SLEEP);
za = kmem_alloc(sizeof(zap_attribute_t), KM_SLEEP);
basezc = kmem_alloc(sizeof(zap_cursor_t), KM_SLEEP);
baseza = kmem_alloc(sizeof(zap_attribute_t), KM_SLEEP);
source = kmem_alloc(MAXNAMELEN + strlen(MOS_DIR_NAME) + 1, KM_SLEEP);
VERIFY(nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP) == 0);
rw_enter(&dp->dp_config_rwlock, RW_READER);
for (dd = startdd; dd != NULL; dd = dd->dd_parent) {
zap_cursor_t basezc;
zap_attribute_t baseza;
nvlist_t *sp_nvp;
uint64_t n;
char source[MAXNAMELEN];
if (dd->dd_phys->dd_deleg_zapobj &&
(zap_count(mos, dd->dd_phys->dd_deleg_zapobj,
@ -323,32 +328,30 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
continue;
}
for (zap_cursor_init(&basezc, mos,
for (zap_cursor_init(basezc, mos,
dd->dd_phys->dd_deleg_zapobj);
zap_cursor_retrieve(&basezc, &baseza) == 0;
zap_cursor_advance(&basezc)) {
zap_cursor_t zc;
zap_attribute_t za;
zap_cursor_retrieve(basezc, baseza) == 0;
zap_cursor_advance(basezc)) {
nvlist_t *perms_nvp;
ASSERT(baseza.za_integer_length == 8);
ASSERT(baseza.za_num_integers == 1);
ASSERT(baseza->za_integer_length == 8);
ASSERT(baseza->za_num_integers == 1);
VERIFY(nvlist_alloc(&perms_nvp,
NV_UNIQUE_NAME, KM_SLEEP) == 0);
for (zap_cursor_init(&zc, mos, baseza.za_first_integer);
zap_cursor_retrieve(&zc, &za) == 0;
zap_cursor_advance(&zc)) {
for (zap_cursor_init(zc, mos, baseza->za_first_integer);
zap_cursor_retrieve(zc, za) == 0;
zap_cursor_advance(zc)) {
VERIFY(nvlist_add_boolean(perms_nvp,
za.za_name) == 0);
za->za_name) == 0);
}
zap_cursor_fini(&zc);
VERIFY(nvlist_add_nvlist(sp_nvp, baseza.za_name,
zap_cursor_fini(zc);
VERIFY(nvlist_add_nvlist(sp_nvp, baseza->za_name,
perms_nvp) == 0);
nvlist_free(perms_nvp);
}
zap_cursor_fini(&basezc);
zap_cursor_fini(basezc);
dsl_dir_name(dd, source);
VERIFY(nvlist_add_nvlist(*nvp, source, sp_nvp) == 0);
@ -356,6 +359,12 @@ dsl_deleg_get(const char *ddname, nvlist_t **nvp)
}
rw_exit(&dp->dp_config_rwlock);
kmem_free(source, MAXNAMELEN + strlen(MOS_DIR_NAME) + 1);
kmem_free(baseza, sizeof(zap_attribute_t));
kmem_free(basezc, sizeof(zap_cursor_t));
kmem_free(za, sizeof(zap_attribute_t));
kmem_free(zc, sizeof(zap_cursor_t));
dsl_dir_close(startdd, FTAG);
return (0);
}