9p: fix readlink

I do not know if you've looked on the patch, but unfortunately it is incorrect. A suggested better version is in this email (the old version didn't work in case the user provided buffer was not long enough - it incorrectly appended null byte on a position of last char, and thus broke the contract of the readlink method). However, I'm still not sure this is 100% correct thing to do, I think readlink is supposed to return buffer without last null byte in all cases, but we do return last null byte (even the old version).. on the other hand it is likely unspecified what is in the remaining part of the buffer, so null character may be fine there ;): Signed-off-by: Martin Stava <martin.stava@gmail.com> Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

9p: fix readlink
I do not know if you've looked on the patch, but unfortunately it is incorrect. A suggested better version is in this email (the old version didn't work in case the user provided buffer was not long enough - it incorrectly appended null byte on a position of last char, and thus broke the contract of the readlink method). However, I'm still not sure this is 100% correct thing to do, I think readlink is supposed to return buffer without last null byte in all cases, but we do return last null byte (even the old version).. on the other hand it is likely unspecified what is in the remaining part of the buffer, so null character may be fine there ;): Signed-off-by: Martin Stava <martin.stava@gmail.com> Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Martin Stava · Eric Van Hensbergen
1 parent f91b90993f
Showing 1 changed file with 2 additions and 3 deletions Side-by-side Diff
fs/9p/vfs_inode.c
@@ -994,8 +994,7 @@
 	P9_DPRINTK(P9_DEBUG_VFS,
 		"%s -> %s (%s)\n", dentry->d_name.name, st->extension, buffer);
  
-	retval = buflen;
-
+	retval = strnlen(buffer, buflen);
 done:
 	kfree(st);
 	return retval;
@@ -1062,7 +1061,7 @@
 			__putname(link);
 			link = ERR_PTR(len);
 		} else
-			link[len] = 0;
+			link[min(len, PATH_MAX-1)] = 0;
 	}
 	nd_set_link(nd, link);
...	...	@@ -994,8 +994,7 @@
994	994	P9_DPRINTK(P9_DEBUG_VFS,
995	995	"%s -> %s (%s)\n", dentry->d_name.name, st->extension, buffer);
996	996
997		- retval = buflen;
998		-
	997	+ retval = strnlen(buffer, buflen);
999	998	done:
1000	999	kfree(st);
1001	1000	return retval;
...	...	@@ -1062,7 +1061,7 @@
1062	1061	__putname(link);
1063	1062	link = ERR_PTR(len);
1064	1063	} else
1065		- link[len] = 0;
	1064	+ link[min(len, PATH_MAX-1)] = 0;
1066	1065	}
1067	1066	nd_set_link(nd, link);
1068	1067