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Use a write lock during ossl_provider_find()

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A "find" operation on a stack can end up sorting the underlying stack. In
this case it is necessary to use a "write" lock to synchronise access to
the stack across multiple threads.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16980)
This commit is contained in:
Matt Caswell 2021-11-09 14:32:14 +00:00
parent 1e8ed3e596
commit 4aced11785
2 changed files with 9 additions and 2 deletions
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6
crypto/provider_core.c
View File

@ -423,7 +423,11 @@ OSSL_PROVIDER *ossl_provider_find(OSSL_LIB_CTX *libctx, const char *name,
#endif
tmpl.name = (char *)name;
if (!CRYPTO_THREAD_read_lock(store->lock))
/*
* A "find" operation can sort the stack, and therefore a write lock is
* required.
*/
if (!CRYPTO_THREAD_write_lock(store->lock))
return NULL;
if ((i = sk_OSSL_PROVIDER_find(store->providers, &tmpl)) != -1)
prov = sk_OSSL_PROVIDER_value(store->providers, i);

5
doc/man3/DEFINE_STACK_OF.pod
View File

@ -178,7 +178,10 @@ where a comparison function has been specified, I<sk> is sorted and
B<sk_I<TYPE>_find>() returns the index of a matching element or B<-1> if there
is no match. Note that, in this case the comparison function will usually
compare the values pointed to rather than the pointers themselves and
the order of elements in I<sk> can change.
the order of elements in I<sk> can change. Note that because the stack may be
sorted as the result of a B<sk_I<TYPE>_find>() call, if a lock is being used to
synchronise access to the stack across multiple threads, then that lock must be
a "write" lock.
B<sk_I<TYPE>_find_ex>() operates like B<sk_I<TYPE>_find>() except when a
comparison function has been specified and no matching element is found.