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From 031bb5a5d0d950253b68138b498dc93be69a64cb Mon Sep 17 00:00:00 2001
From: Matthias Gerstner <matthias.gerstner@suse.de>
Date: Wed, 27 Dec 2023 14:01:59 +0100
Subject: [PATCH] pam_namespace: protect_dir(): use O_DIRECTORY to prevent
local DoS situations
Without O_DIRECTORY the path crawling logic is subject to e.g. FIFOs
being placed in user controlled directories, causing the PAM module to
block indefinitely during `openat()`.
Pass O_DIRECTORY to cause the `openat()` to fail if the path does not
refer to a directory.
With this the check whether the final path element is a directory
becomes unnecessary, drop it.
Upstream-Status: Backport [https://github.com/linux-pam/linux-pam/commit/031bb5a5d0d950253b68138b498dc93be69a64cb]
CVE: CVE-2024-22365
Signed-off-by: Vijay Anusuri <vanusuri@mvista.com>
---
modules/pam_namespace/pam_namespace.c | 18 +-----------------
1 file changed, 1 insertion(+), 17 deletions(-)
diff --git a/modules/pam_namespace/pam_namespace.c b/modules/pam_namespace/pam_namespace.c
index 2528cff86..f72d67189 100644
--- a/modules/pam_namespace/pam_namespace.c
+++ b/modules/pam_namespace/pam_namespace.c
@@ -1201,7 +1201,7 @@ static int protect_dir(const char *path, mode_t mode, int do_mkdir,
int dfd = AT_FDCWD;
int dfd_next;
int save_errno;
- int flags = O_RDONLY;
+ int flags = O_RDONLY | O_DIRECTORY;
int rv = -1;
struct stat st;
@@ -1255,22 +1255,6 @@ static int protect_dir(const char *path, mode_t mode, int do_mkdir,
rv = openat(dfd, dir, flags);
}
- if (rv != -1) {
- if (fstat(rv, &st) != 0) {
- save_errno = errno;
- close(rv);
- rv = -1;
- errno = save_errno;
- goto error;
- }
- if (!S_ISDIR(st.st_mode)) {
- close(rv);
- errno = ENOTDIR;
- rv = -1;
- goto error;
- }
- }
-
if (flags & O_NOFOLLOW) {
/* we are inside user-owned dir - protect */
if (protect_mount(rv, p, idata) == -1) {
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