From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Mon, 24 Feb 2025 19:07:05 +0000 (+0100)
Subject: shared: let strbuf_str never fail
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2b475981783d5eba139df1c093c8933f7428d663;p=thirdparty%2Fkmod.git

shared: let strbuf_str never fail

The strbuf functionality is always used to create C strings, so already
reserve an extra byte for NUL whenever size allocations occur.

Together with the fact that strbuf_str already returns a const char *,
an empty strbuf may return an unmodifiable empty string.

This renders all strbuf_str return value checks obsolete.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Link: https://github.com/kmod-project/kmod/pull/296
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
---

diff --git a/libkmod/libkmod-index.c b/libkmod/libkmod-index.c
index ae784d6e..cc11f4d3 100644
--- a/libkmod/libkmod-index.c
+++ b/libkmod/libkmod-index.c
@@ -534,7 +534,7 @@ static void index_searchwild__all(struct index_node_f *node, int j, struct strbu
 	if (node->values) {
 		const char *s = strbuf_str(buf);
 
-		if (s != NULL && fnmatch(s, subkey, 0) == 0)
+		if (fnmatch(s, subkey, 0) == 0)
 			index_searchwild__allvalues(node, out);
 		else
 			index_close(node);
@@ -997,7 +997,7 @@ static void index_mm_searchwild_all(struct index_mm_node *node, int j, struct st
 	if (node->value_count > 0) {
 		const char *s = strbuf_str(buf);
 
-		if (s != NULL && fnmatch(s, subkey, 0) == 0)
+		if (fnmatch(s, subkey, 0) == 0)
 			index_mm_searchwild_allvalues(node, out);
 	}
 
diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index dc660f24..ff04ee19 100644
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -1835,8 +1835,6 @@ static struct kmod_list *kmod_module_info_append_hex(struct kmod_list **list,
 		if (!kmod_module_strbuf_pushhex(&sbuf, value, valuelen))
 			goto list_error;
 		hex = strbuf_str(&sbuf);
-		if (hex == NULL)
-			goto list_error;
 
 		n = kmod_module_info_append(list, key, keylen, hex, strlen(hex));
 		if (n == NULL)
diff --git a/shared/strbuf.c b/shared/strbuf.c
index 6ce1f05e..8e6dd72d 100644
--- a/shared/strbuf.c
+++ b/shared/strbuf.c
@@ -36,13 +36,13 @@ static bool buf_realloc(struct strbuf *buf, size_t sz)
 
 bool strbuf_reserve_extra(struct strbuf *buf, size_t n)
 {
-	if (uaddsz_overflow(buf->used, n, &n) || n > SIZE_MAX - BUF_STEP)
+	if (uaddsz_overflow(buf->used, n, &n) || n >= SIZE_MAX - BUF_STEP)
 		return false;
 
-	if (n <= buf->size)
+	if (n < buf->size)
 		return true;
 
-	if (n % BUF_STEP)
+	if (++n % BUF_STEP)
 		n = ((n / BUF_STEP) + 1) * BUF_STEP;
 
 	return buf_realloc(buf, n);
@@ -64,11 +64,11 @@ void strbuf_release(struct strbuf *buf)
 
 const char *strbuf_str(struct strbuf *buf)
 {
-	if (!buf->used || buf->bytes[buf->used - 1]) {
-		if (!strbuf_reserve_extra(buf, 1))
-			return NULL;
+	if (!buf->used)
+		return "";
+
+	if (buf->bytes[buf->used - 1])
 		buf->bytes[buf->used] = '\0';
-	}
 	return buf->bytes;
 }
 
diff --git a/tools/depmod.c b/tools/depmod.c
index dcc7acbe..5db9701c 100644
--- a/tools/depmod.c
+++ b/tools/depmod.c
@@ -1362,7 +1362,7 @@ static int depmod_modules_search_dir(struct depmod *depmod, DIR *d, struct strbu
 		namelen = strlen(name);
 
 		if (!strbuf_pushchars(path, name) ||
-		    /* Ensure space for (possible) '/' or '\0' */
+		    /* Ensure space for (possible) '/' */
 		    !strbuf_reserve_extra(path, 1)) {
 			err = -ENOMEM;
 			ERR("No memory\n");
@@ -2360,8 +2360,7 @@ static int output_symbols_bin(struct depmod *depmod, FILE *out)
 
 		strbuf_shrink_to(&salias, baselen);
 
-		if (!strbuf_pushchars(&salias, sym->name) ||
-		    !strbuf_reserve_extra(&salias, 1)) {
+		if (!strbuf_pushchars(&salias, sym->name)) {
 			ret = -ENOMEM;
 			goto err_alloc;
 		}