Fix stack vn_open()

We should not put a 4k maxpathlen buffer on the stack, instead
locate it to the heap.  Even in user space we run ztest with 8K
stacks to verify correctness

Signed-off-by: Brian Behlendorf <[email protected]>

1 files changed, 17 insertions, 6 deletions

diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index 4bd08cdd4..0559347e9 100644
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -517,10 +517,12 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
 	int fd;
 	vnode_t *vp;
 	int old_umask;
-	char realpath[MAXPATHLEN];
+	char *realpath;
 	struct stat64 st;
 	int err;
 
+	realpath = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
+
 	/*
 	 * If we're accessing a real disk from userland, we need to use
 	 * the character interface to avoid caching.  This is particularly
@@ -534,11 +536,16 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
 	if (strncmp(path, "/dev/", 5) == 0) {
 		char *dsk;
 		fd = open64(path, O_RDONLY);
-		if (fd == -1)
-			return (errno);
+		if (fd == -1) {
+			err = errno;
+			free(realpath);
+			return (err);
+		}
 		if (fstat64(fd, &st) == -1) {
+			err = errno;
 			close(fd);
-			return (errno);
+			free(realpath);
+			return (err);
 		}
 		close(fd);
 		(void) sprintf(realpath, "%s", path);
@@ -548,8 +555,11 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
 			    dsk + 1);
 	} else {
 		(void) sprintf(realpath, "%s", path);
-		if (!(flags & FCREAT) && stat64(realpath, &st) == -1)
-			return (errno);
+		if (!(flags & FCREAT) && stat64(realpath, &st) == -1) {
+			err = errno;
+			free(realpath);
+			return (err);
+		}
 	}
 
 	if (flags & FCREAT)
@@ -560,6 +570,7 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
 	 * FREAD and FWRITE to the corresponding O_RDONLY, O_WRONLY, and O_RDWR.
 	 */
 	fd = open64(realpath, flags - FREAD, mode);
+	free(realpath);
 
 	if (flags & FCREAT)
 		(void) umask(old_umask);