sysfsutils/0007-fix-sysfs_get_link.patch

From b93c115b71c08a2f19262e6adccfdb5a5e5b2a78 Mon Sep 17 00:00:00 2001
From: Christopher Engelhard <ce@lcts.de>
Date: Tue, 28 Jul 2020 17:35:05 +0200
Subject: [PATCH 7/8] Fix bug in sysfs_get_link

This fixes RHBZ #447220/Debian Bug #481015 by applying the patch
provided in those bugs.
---
 lib/sysfs_utils.c | 128 +++++++++++++++++++++++++++-------------------
 1 file changed, 76 insertions(+), 52 deletions(-)

diff --git a/lib/sysfs_utils.c b/lib/sysfs_utils.c
index bddf722..e9bc555 100644
--- a/lib/sysfs_utils.c
+++ b/lib/sysfs_utils.c
@@ -117,80 +117,104 @@ int sysfs_get_link(const char *path, char *target, size_t len)
 {
 	char devdir[SYSFS_PATH_MAX];
 	char linkpath[SYSFS_PATH_MAX];
-	char temp_path[SYSFS_PATH_MAX];
-	char *d = NULL, *s = NULL;
-	int slashes = 0, count = 0;
+	char *d, *s;
+	int count;
 
 	if (!path || !target || len == 0) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	memset(devdir, 0, SYSFS_PATH_MAX);
-	memset(linkpath, 0, SYSFS_PATH_MAX);
-	memset(temp_path, 0, SYSFS_PATH_MAX);
-	safestrcpy(devdir, path);
-
-	if ((readlink(path, linkpath, SYSFS_PATH_MAX)) < 0) {
+	count = readlink(path, linkpath, SYSFS_PATH_MAX);
+	if (count < 0)
 		return -1;
-	}
-	d = linkpath;
+	else
+		linkpath[count] = '\0';
 	/*
 	 * Three cases here:
 	 * 1. relative path => format ../..
 	 * 2. absolute path => format /abcd/efgh
 	 * 3. relative path _from_ this dir => format abcd/efgh
 	 */
-	switch (*d) {
-		case '.':
+	if (*linkpath == '/') {
+		/* absolute path - copy as is */
+		safestrcpymax(target, linkpath, len);
+		return 0;
+	}
+
+	safestrcpy(devdir, path);
+	s = strrchr(devdir, '/');
+	if (s == NULL)
+		s = devdir - 1;
+	d = linkpath;
+	while (*d == '.') {
+		if (*(d+1) == '/') {
 			/*
 			 * handle the case where link is of type ./abcd/xxx
 			 */
-			safestrcpy(temp_path, devdir);
-			if (*(d+1) == '/')
-				d += 2;
-			else if (*(d+1) == '.')
-				goto parse_path;
-			s = strrchr(temp_path, '/');
-			if (s != NULL)
-				safestrcpy(s+1, d);
-			else
-				safestrcpy(temp_path, d);
-			safestrcpymax(target, temp_path, len);
-			break;
+			d += 2;
+			while (*d == '/')
+				d++;
+			continue;
+		} else if (*(d+1) != '.' || *(d+2) != '/')
 			/*
-			 * relative path, getting rid of leading "../.."
+			 * relative path from this directory, starting
+			 * with a hidden directory
 			 */
-parse_path:
-			while (*d == '/' || *d == '.') {
-				if (*d == '/')
-					slashes++;
-				d++;
-			}
-			d--;
-			s = &devdir[strlen(devdir)-1];
-			while (s != NULL && count != (slashes+1)) {
+			break;
+
+		/*
+		 * relative path, getting rid of leading "../.."; must
+		 * be careful here since any path component of devdir
+		 * could be a symlink again
+		 */
+		for (;;) {
+			while (s > devdir && *s == '/') {
 				s--;
-				if (*s == '/')
-					count++;
+				if (*s == '.'
+				    && (s == devdir || *(s-1) == '/'))
+					s--;
 			}
-			safestrcpymax(s, d, (SYSFS_PATH_MAX-strlen(devdir)));
-			safestrcpymax(target, devdir, len);
-			break;
-		case '/':
-			/* absolute path - copy as is */
-			safestrcpymax(target, linkpath, len);
+			*(s+1) = '\0';
+			if (*devdir == '\0' || sysfs_path_is_link(devdir))
+				/*
+				 * condition will be true eventually
+				 * because we already know that all
+				 * but the last component of path
+				 * resolve to a directory
+				 */
+				break;
+			if (sysfs_get_link(devdir, devdir, SYSFS_PATH_MAX))
+				return -1;
+			s = devdir + strlen(devdir) - 1;
+		}
+		while (s >= devdir) {
+			if (*s == '/') {
+				if (*(s+1) != '.' || *(s+2) != '.'
+				    || *(s+3) != '\0') {
+					d += 3;
+					while (*d == '/')
+						d++;
+				} else
+					s += 2;
+				break;
+			}
+			s--;
+		}
+		if (s < devdir || *(s+1) == '\0')
 			break;
-		default:
-			/* relative path from this directory */
-			safestrcpy(temp_path, devdir);
-			s = strrchr(temp_path, '/');
-			if (s != NULL)
-				safestrcpy(s+1, linkpath);
-			else
-				safestrcpy(temp_path, linkpath);
-			safestrcpymax(target, temp_path, len);
 	}
+
+	/*
+	 * appending to devdir a slash and the (possibly shortened)
+	 * relative path to the link source
+	 */
+	s++;
+	if (s > devdir && *s == '\0')
+		*s++ = '/';
+	*s = '\0';
+	safestrcpymax(s, d, SYSFS_PATH_MAX-(s-devdir));
+	safestrcpymax(target, devdir, len);
 	return 0;
 }
 
-- 
2.28.0