From a7f9759ef8ce354ab2ad420d4a8c5b4260d491fc Mon Sep 17 00:00:00 2001
From: vegbir <[email protected]>
Date: Thu, 27 Jul 2023 07:24:18 +0000
Subject: [PATCH 05/15] fix concurrency problem

Signed-off-by: vegbir <[email protected]>
---
 src/cgroups/cgroup_utils.c | 21 +++++++++++++--------
 src/cgroups/cgroup_utils.h |  2 +-
 src/proc_fuse.c            |  3 +++
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/cgroups/cgroup_utils.c b/src/cgroups/cgroup_utils.c
index 83e4cbf..1224971 100644
--- a/src/cgroups/cgroup_utils.c
+++ b/src/cgroups/cgroup_utils.c
@@ -512,23 +512,28 @@ static char *copy_to_eol(char *p)
 	return sret;
 }
 
-static void batch_realloc(char **mem, size_t oldlen, size_t newlen)
+char *batch_realloc(char *mem, size_t oldlen, size_t newlen)
 {
 	int newbatches = (newlen / BATCH_SIZE) + 1;
 	int oldbatches = (oldlen / BATCH_SIZE) + 1;
 
-	if (!*mem || newbatches > oldbatches) {
-		*mem = must_realloc(*mem, newbatches * BATCH_SIZE);
+	if (!mem || newbatches > oldbatches) {
+		char *tmp;
+		tmp = must_realloc(mem, newbatches * BATCH_SIZE);
+		return tmp;
 	}
+	return mem;
 }
 
-void append_line(char **dest, size_t oldlen, char *new, size_t newlen)
+char *append_line(char *dest, size_t oldlen, char *new, size_t newlen)
 {
+	char *tmp;
 	size_t full = oldlen + newlen;
 
-	batch_realloc(dest, oldlen, full + 1);
+	tmp = batch_realloc(dest, oldlen, full + 1);
 
-	memcpy(*dest + oldlen, new, newlen + 1);
+	memcpy(tmp + oldlen, new, newlen + 1);
+	return tmp;
 }
 
 static inline void drop_trailing_newlines(char *s)
@@ -552,7 +557,7 @@ char *read_file(const char *fnam)
 	if (!f)
 		return NULL;
 	while ((linelen = getline(&line, &len, f)) != -1) {
-		append_line(&buf, fulllen, line, linelen);
+		buf = append_line(buf, fulllen, line, linelen);
 		fulllen += linelen;
 	}
 	return buf;
@@ -682,7 +687,7 @@ char *readat_file(int dirfd, const char *path)
 	move_fd(fd);
 
 	while ((linelen = getline(&line, &len, f)) != -1) {
-		append_line(&buf, fulllen, line, linelen);
+		buf = append_line(buf, fulllen, line, linelen);
 		fulllen += linelen;
 	}
 
diff --git a/src/cgroups/cgroup_utils.h b/src/cgroups/cgroup_utils.h
index f431686..d4c8598 100644
--- a/src/cgroups/cgroup_utils.h
+++ b/src/cgroups/cgroup_utils.h
@@ -70,7 +70,7 @@ extern size_t strlcat(char *d, const char *s, size_t n);
 #endif
 
 extern FILE *fopen_cloexec(const char *path, const char *mode);
-extern void append_line(char **dest, size_t oldlen, char *new, size_t newlen);
+extern char *append_line(char *dest, size_t oldlen, char *new, size_t newlen);
 extern char *read_file(const char *fnam);
 extern char *readat_file(int fd, const char *path);
 extern char *read_file_strip_newline(const char *fnam);
diff --git a/src/proc_fuse.c b/src/proc_fuse.c
index ed70ea7..0af559f 100644
--- a/src/proc_fuse.c
+++ b/src/proc_fuse.c
@@ -1747,6 +1747,9 @@ __lxcfs_fuse_ops int proc_read(const char *path, char *buf, size_t size,
 {
 	struct file_info *f = INTTYPE_TO_PTR(fi->fh);
 
+	if (!f->buf)
+		return -EINVAL;
+
 	switch (f->type) {
 	case LXC_TYPE_PROC_MEMINFO:
 		if (liblxcfs_functional())
-- 
2.41.0