hash: Fix compilation error on Fedora 34 with GCC 11 and -O0.

With newest version of GCC, OVS fails to compile with -O0 due to
false-positive overread detection in hash-related functions.  Those
function declares "const uint32_t p[]" as argument and it throws off
the compiler into thinking that it reads from memory region of size 0.

To fix that behavior, a change in argument declaration needs to be made:
instead of using "[]" notation for a pointer, simply use "*".

The reported error in question:

lib/conntrack.c: In function ‘conn_key_hash’:
lib/conntrack.c:2154:12: error: ‘hash_words’ reading 4 bytes \
                   from a region of size 0 [-Werror=stringop-overread]
 2154| return hash_words((uint32_t *) (&key->dst + 1),
     |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 2155|                   (uint32_t *) (key + 1) - (uint32_t *) (&key->dst + 1),
     |                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 2156|                   hash);
     |                   ~~~~~
lib/conntrack.c:2154:12: note: referencing argument 1 \
        of type ‘const uint32_t *’ {aka ‘const unsigned int *’}
In file included from lib/packets.h:31,
                 from lib/ct-dpif.h:21,
                 from lib/conntrack.h:23,
                 from lib/conntrack.c:26:
lib/hash.h:294:1: note: in a call to function ‘hash_words’
  294 | hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
      | ^~~~~~~~~~

Signed-off-by: Guzowski Adrian <adrian.guzowski@exatel.pl>
Tested-by: Numan Siddique <numans@ovn.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

2 files changed, 11 insertions, 11 deletions

diff --git a/lib/hash.c b/lib/hash.c
index 06f83395c..c722f3c3c 100644
--- a/lib/hash.c
+++ b/lib/hash.c
@@ -61,13 +61,13 @@ hash_double(double x, uint32_t basis)
 }
 
 uint32_t
-hash_words__(const uint32_t p[], size_t n_words, uint32_t basis)
+hash_words__(const uint32_t *p, size_t n_words, uint32_t basis)
 {
     return hash_words_inline(p, n_words, basis);
 }
 
 uint32_t
-hash_words64__(const uint64_t p[], size_t n_words, uint32_t basis)
+hash_words64__(const uint64_t *p, size_t n_words, uint32_t basis)
 {
     return hash_words64_inline(p, n_words, basis);
 }
diff --git a/lib/hash.h b/lib/hash.h
index eb3776500..60a39a40b 100644
--- a/lib/hash.h
+++ b/lib/hash.h
@@ -235,7 +235,7 @@ hash_words_inline(const uint32_t p_[], size_t n_words, uint32_t basis)
 /* A simpler version for 64-bit data.
  * 'n_words' is the count of 64-bit words, basis is 64 bits. */
 static inline uint32_t
-hash_words64_inline(const uint64_t p[], size_t n_words, uint32_t basis)
+hash_words64_inline(const uint64_t *p, size_t n_words, uint32_t basis)
 {
     uint64_t hash1 = basis;
     uint64_t hash2 = 0;
@@ -284,14 +284,14 @@ static inline uint32_t hash_pointer(const void *p, uint32_t basis)
 }
 #endif
 
-uint32_t hash_words__(const uint32_t p[], size_t n_words, uint32_t basis);
-uint32_t hash_words64__(const uint64_t p[], size_t n_words, uint32_t basis);
+uint32_t hash_words__(const uint32_t *p, size_t n_words, uint32_t basis);
+uint32_t hash_words64__(const uint64_t *p, size_t n_words, uint32_t basis);
 
 /* Inline the larger hash functions only when 'n_words' is known to be
  * compile-time constant. */
 #if __GNUC__ >= 4
 static inline uint32_t
-hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
+hash_words(const uint32_t *p, size_t n_words, uint32_t basis)
 {
     if (__builtin_constant_p(n_words)) {
         return hash_words_inline(p, n_words, basis);
@@ -301,7 +301,7 @@ hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
 }
 
 static inline uint32_t
-hash_words64(const uint64_t p[], size_t n_words, uint32_t basis)
+hash_words64(const uint64_t *p, size_t n_words, uint32_t basis)
 {
     if (__builtin_constant_p(n_words)) {
         return hash_words64_inline(p, n_words, basis);
@@ -313,26 +313,26 @@ hash_words64(const uint64_t p[], size_t n_words, uint32_t basis)
 #else
 
 static inline uint32_t
-hash_words(const uint32_t p[], size_t n_words, uint32_t basis)
+hash_words(const uint32_t *p, size_t n_words, uint32_t basis)
 {
     return hash_words__(p, n_words, basis);
 }
 
 static inline uint32_t
-hash_words64(const uint64_t p[], size_t n_words, uint32_t basis)
+hash_words64(const uint64_t *p, size_t n_words, uint32_t basis)
 {
     return hash_words64__(p, n_words, basis);
 }
 #endif
 
 static inline uint32_t
-hash_bytes32(const uint32_t p[], size_t n_bytes, uint32_t basis)
+hash_bytes32(const uint32_t *p, size_t n_bytes, uint32_t basis)
 {
     return hash_words(p, n_bytes / 4, basis);
 }
 
 static inline uint32_t
-hash_bytes64(const uint64_t p[], size_t n_bytes, uint32_t basis)
+hash_bytes64(const uint64_t *p, size_t n_bytes, uint32_t basis)
 {
     return hash_words64(p, n_bytes / 8, basis);
 }