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Find fusermount using execvp #32

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Find fusermount using execvp #32

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35eeefb
Find fusermount on $PATH
probonopd May 9, 2024
7239a8a
Merge branch 'main' into find-fusermount-on-path
probonopd Aug 7, 2024
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61 changes: 35 additions & 26 deletions patches/libfuse/mount.c.diff
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
diff --git a/lib/mount.c b/lib/mount.c
index d71e6fc55..acc1711ff 100644
index d71e6fc55..1c70c8c87 100644
--- a/lib/mount.c
+++ b/lib/mount.c
@@ -41,7 +41,6 @@
Expand All @@ -10,12 +10,12 @@ index d71e6fc55..acc1711ff 100644
#define FUSE_COMMFD_ENV "_FUSE_COMMFD"

#ifndef HAVE_FORK
@@ -117,17 +116,79 @@ static const struct fuse_opt fuse_mount_opts[] = {
@@ -117,17 +116,87 @@ static const struct fuse_opt fuse_mount_opts[] = {
FUSE_OPT_END
};

+int fileExists(const char* path);
+char* findBinaryInFusermountDir(const char* binaryName);
+char* findBinaryOnPath(const char* binaryName);
+
+int fileExists(const char* path) {
+ FILE* file = fopen(path, "r");
Expand All @@ -26,46 +26,54 @@ index d71e6fc55..acc1711ff 100644
+ return 0;
+}
+
+char* findBinaryInFusermountDir(const char* binaryName) {
+ // For security reasons, we do not search the binary on the $PATH;
+ // instead, we check if the binary exists in FUSERMOUNT_DIR
+ // as defined in meson.build
+ char* binaryPath = malloc(strlen(FUSERMOUNT_DIR) + strlen(binaryName) + 2);
+ strcpy(binaryPath, FUSERMOUNT_DIR);
+ strcat(binaryPath, "/");
+ strcat(binaryPath, binaryName);
+ if (fileExists(binaryPath)) {
+ return binaryPath;
+ }
+char* findBinaryOnPath(const char* binaryName) {
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I think we agreed on using execvp instead of manually tracing the PATH?

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@probonopd probonopd Aug 8, 2024 •
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You are spot on. We should use that instead. As I summarized in #32 (comment). If you agree with the points there, could you please help me implement them? That would really be a great contribution. Thanks!

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I can provide the implementation, but it'll take a while until I'll get to it.

#32

If we choose to utilize execvp, those points need to be considered.

+ const char* path = getenv("PATH");
+ const char* delimiter = ":";
+ char* pathCopy = strdup(path); // Create a copy of the PATH string
+
+ // If the binary does not exist in FUSERMOUNT_DIR, return NULL
+ return NULL;
+ char* directory = strtok(pathCopy, delimiter);
+ while (directory != NULL) {
+ char fullPath[256];
+ snprintf(fullPath, sizeof(fullPath), "%s/%s", directory, binaryName);
+
+ if (fileExists(fullPath)) {
+ free(pathCopy); // Release the memory allocated by strdup
+ return strdup(fullPath);
+ }
+
+ directory = strtok(NULL, delimiter);
+ }
+
+ free(pathCopy); // Release the memory allocated by strdup
+ return NULL; // File not found on the $PATH
+}
+
+static const char *fuse_mount_prog(void)
+{
+ // Check if the FUSERMOUNT_PROG environment variable is set and if so, use it
+ const char *prog = getenv("FUSERMOUNT_PROG");
+ // Find the binary with the name specified in FUSERMOUNT_PROG on the $PATH
+ prog = findBinaryOnPath(prog);
+ if (prog) {
+ if (access(prog, X_OK) == 0)
+ return prog;
+ }
+
+ // Check if there is a binary "fusermount3"
+ prog = findBinaryInFusermountDir("fusermount3");
+ // Check if there is a binary "fusermount3" on the $PATH
+ prog = findBinaryOnPath("fusermount3");
+ if (access(prog, X_OK) == 0)
+ return prog;
+
+ // Check if there is a binary called "fusermount"
+ // Check if there is a binary called "fusermount" on the $PATH
+ // This is known to work for our purposes
+ prog = findBinaryInFusermountDir("fusermount");
+ prog = findBinaryOnPath("fusermount");
+ if (access(prog, X_OK) == 0)
+ return prog;
+
+ // For i = 4...99, check if there is a binary called "fusermount" + i
+ // For i = 4...99, check if there is a binary called "fusermount" + i on the $PATH
+ // It is not yet known whether this will work for our purposes, but it is better than not even attempting
+ for (int i = 4; i < 100; i++) {
+ prog = findBinaryInFusermountDir("fusermount" + i);
+ prog = findBinaryOnPath("fusermount" + i);
+ if (access(prog, X_OK) == 0)
+ return prog;
+ }
Expand Down Expand Up @@ -93,7 +101,7 @@ index d71e6fc55..acc1711ff 100644
exec_fusermount(argv);
_exit(1);
} else if (pid != -1)
@@ -300,7 +361,7 @@ void fuse_kern_unmount(const char *mountpoint, int fd)
@@ -300,7 +369,7 @@ void fuse_kern_unmount(const char *mountpoint, int fd)
return;

if(pid == 0) {
Expand All @@ -102,7 +110,7 @@ index d71e6fc55..acc1711ff 100644
"--", mountpoint, NULL };

exec_fusermount(argv);
@@ -346,7 +407,7 @@ static int setup_auto_unmount(const char *mountpoint, int quiet)
@@ -346,7 +415,7 @@ static int setup_auto_unmount(const char *mountpoint, int quiet)
}
}

Expand All @@ -111,7 +119,7 @@ index d71e6fc55..acc1711ff 100644
argv[a++] = "--auto-unmount";
argv[a++] = "--";
argv[a++] = mountpoint;
@@ -407,7 +468,7 @@ static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
@@ -407,7 +476,7 @@ static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
}
}

Expand All @@ -120,11 +128,12 @@ index d71e6fc55..acc1711ff 100644
if (opts) {
argv[a++] = "-o";
argv[a++] = opts;
@@ -421,7 +482,7 @@ static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
@@ -421,7 +490,7 @@ static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
snprintf(env, sizeof(env), "%i", fds[0]);
setenv(FUSE_COMMFD_ENV, env, 1);
exec_fusermount(argv);
- perror("fuse: failed to exec fusermount3");
+ perror("fuse: failed to exec fusermount");
_exit(1);
}

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