gcc 11 cleanup

Compiling with gcc 11.1.0 produces three new warnings.
Change the code slightly to avoid them.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Attila Fülöp <attila@fueloep.org>
Closes #12130
Closes #12188
Closes #12237

contrib/pam_zfs_key/pam_zfs_key.c

@@ -82,7 +82,11 @@ alloc_pw_size(size_t len)
 		return (NULL);
 	}
 	pw->len = len;
-	pw->value = malloc(len);
+	/*
+	 * The use of malloc() triggers a spurious gcc 11 -Wmaybe-uninitialized
+	 * warning in the mlock() function call below, so use calloc().
+	 */
+	pw->value = calloc(len, 1);
 	if (!pw->value) {
 		free(pw);
 		return (NULL);
@@ -99,7 +103,11 @@ alloc_pw_string(const char *source)
 		return (NULL);
 	}
 	pw->len = strlen(source) + 1;
-	pw->value = malloc(pw->len);
+	/*
+	 * The use of malloc() triggers a spurious gcc 11 -Wmaybe-uninitialized
+	 * warning in the mlock() function call below, so use calloc().
+	 */
+	pw->value = calloc(pw->len, 1);
 	if (!pw->value) {
 		free(pw);
 		return (NULL);

include/sys/crypto/api.h

@@ -58,7 +58,7 @@ typedef struct {
  */
 
 #define	CRYPTO_MECH_INVALID	((uint64_t)-1)
-extern crypto_mech_type_t crypto_mech2id(crypto_mech_name_t name);
+extern crypto_mech_type_t crypto_mech2id(char *name);
 
 /*
  * Create and destroy context templates.

include/sys/dnode.h

@@ -171,7 +171,7 @@ enum dnode_dirtycontext {
  * example, reading 32 dnodes from a 16k dnode block and all of the spill
  * blocks could issue 33 separate reads. Now suppose those dnodes have size
  * 1024 and therefore don't need spill blocks. Then the worst case number
- * of blocks read is reduced to from 33 to two--one per dnode block.
+ * of blocks read is reduced from 33 to two--one per dnode block.
  *
  * ZFS-on-Linux systems that make heavy use of extended attributes benefit
  * from this feature. In particular, ZFS-on-Linux supports the xattr=sa
@@ -232,8 +232,8 @@ typedef struct dnode_phys {
 	 * Both dn_pad2 and dn_pad3 are protected by the block's MAC. This
 	 * allows us to protect any fields that might be added here in the
 	 * future. In either case, developers will want to check
-	 * zio_crypt_init_uios_dnode() to ensure the new field is being
+	 * zio_crypt_init_uios_dnode() and zio_crypt_do_dnode_hmac_updates()
-	 * protected properly.
+	 * to ensure the new field is being protected and updated properly.
 	 */
 	uint64_t dn_pad3[4];
 

module/os/linux/zfs/zio_crypt.c

@@ -1045,17 +1045,23 @@ zio_crypt_do_dnode_hmac_updates(crypto_context_t ctx, uint64_t version,
     boolean_t should_bswap, dnode_phys_t *dnp)
 {
 	int ret, i;
-	dnode_phys_t *adnp;
+	dnode_phys_t *adnp, tmp_dncore;
+	size_t dn_core_size = offsetof(dnode_phys_t, dn_blkptr);
 	boolean_t le_bswap = (should_bswap == ZFS_HOST_BYTEORDER);
 	crypto_data_t cd;
-	uint8_t tmp_dncore[offsetof(dnode_phys_t, dn_blkptr)];
 
 	cd.cd_format = CRYPTO_DATA_RAW;
 	cd.cd_offset = 0;
 
-	/* authenticate the core dnode (masking out non-portable bits) */
+	/*
-	bcopy(dnp, tmp_dncore, sizeof (tmp_dncore));
+	 * Authenticate the core dnode (masking out non-portable bits).
-	adnp = (dnode_phys_t *)tmp_dncore;
+	 * We only copy the first 64 bytes we operate on to avoid the overhead
+	 * of copying 512-64 unneeded bytes. The compiler seems to be fine
+	 * with that.
+	 */
+	bcopy(dnp, &tmp_dncore, dn_core_size);
+	adnp = &tmp_dncore;
+
 	if (le_bswap) {
 		adnp->dn_datablkszsec = BSWAP_16(adnp->dn_datablkszsec);
 		adnp->dn_bonuslen = BSWAP_16(adnp->dn_bonuslen);
@@ -1065,7 +1071,7 @@ zio_crypt_do_dnode_hmac_updates(crypto_context_t ctx, uint64_t version,
 	adnp->dn_flags &= DNODE_CRYPT_PORTABLE_FLAGS_MASK;
 	adnp->dn_used = 0;
 
-	cd.cd_length = sizeof (tmp_dncore);
+	cd.cd_length = dn_core_size;
 	cd.cd_raw.iov_base = (char *)adnp;
 	cd.cd_raw.iov_len = cd.cd_length;