[ Upstream commit
8a924db2d7b5eb69ba08b1a0af46e9f1359a9bdf ]
When vfs_getattr_nosec() calls a filesystem's getattr interface function
then the 'nosec' should propagate into this function so that
vfs_getattr_nosec() can again be called from the filesystem's gettattr
rather than vfs_getattr(). The latter would add unnecessary security
checks that the initial vfs_getattr_nosec() call wanted to avoid.
Therefore, introduce the getattr flag GETATTR_NOSEC and allow to pass
with the new getattr_flags parameter to the getattr interface function.
In overlayfs and ecryptfs use this flag to determine which one of the
two functions to call.
In a recent code change introduced to IMA vfs_getattr_nosec() ended up
calling vfs_getattr() in overlayfs, which in turn called
security_inode_getattr() on an exiting process that did not have
current->fs set anymore, which then caused a kernel NULL pointer
dereference. With this change the call to security_inode_getattr() can
be avoided, thus avoiding the NULL pointer dereference.
Reported-by: <syzbot+a67fc5321ffb4b311c98@syzkaller.appspotmail.com>
Fixes:
db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version")
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <linux-fsdevel@vger.kernel.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Tyler Hicks <code@tyhicks.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Suggested-by: Christian Brauner <brauner@kernel.org>
Co-developed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Link: https://lore.kernel.org/r/20231002125733.1251467-1-stefanb@linux.vnet.ibm.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
return rc;
}
+static int ecryptfs_do_getattr(const struct path *path, struct kstat *stat,
+ u32 request_mask, unsigned int flags)
+{
+ if (flags & AT_GETATTR_NOSEC)
+ return vfs_getattr_nosec(path, stat, request_mask, flags);
+ return vfs_getattr(path, stat, request_mask, flags);
+}
+
static int ecryptfs_getattr(struct mnt_idmap *idmap,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int flags)
struct kstat lower_stat;
int rc;
- rc = vfs_getattr(ecryptfs_dentry_to_lower_path(dentry), &lower_stat,
- request_mask, flags);
+ rc = ecryptfs_do_getattr(ecryptfs_dentry_to_lower_path(dentry),
+ &lower_stat, request_mask, flags);
if (!rc) {
fsstack_copy_attr_all(d_inode(dentry),
ecryptfs_inode_to_lower(d_inode(dentry)));
type = ovl_path_real(dentry, &realpath);
old_cred = ovl_override_creds(dentry->d_sb);
- err = vfs_getattr(&realpath, stat, request_mask, flags);
+ err = ovl_do_getattr(&realpath, stat, request_mask, flags);
if (err)
goto out;
(!is_dir ? STATX_NLINK : 0);
ovl_path_lower(dentry, &realpath);
- err = vfs_getattr(&realpath, &lowerstat,
- lowermask, flags);
+ err = ovl_do_getattr(&realpath, &lowerstat, lowermask,
+ flags);
if (err)
goto out;
ovl_path_lowerdata(dentry, &realpath);
if (realpath.dentry) {
- err = vfs_getattr(&realpath, &lowerdatastat,
- lowermask, flags);
+ err = ovl_do_getattr(&realpath, &lowerdatastat,
+ lowermask, flags);
if (err)
goto out;
} else {
return ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC));
}
+static inline int ovl_do_getattr(const struct path *path, struct kstat *stat,
+ u32 request_mask, unsigned int flags)
+{
+ if (flags & AT_GETATTR_NOSEC)
+ return vfs_getattr_nosec(path, stat, request_mask, flags);
+ return vfs_getattr(path, stat, request_mask, flags);
+}
+
/* util.c */
int ovl_want_write(struct dentry *dentry);
void ovl_drop_write(struct dentry *dentry);
idmap = mnt_idmap(path->mnt);
if (inode->i_op->getattr)
return inode->i_op->getattr(idmap, path, stat,
- request_mask, query_flags);
+ request_mask,
+ query_flags | AT_GETATTR_NOSEC);
generic_fillattr(idmap, request_mask, inode, stat);
return 0;
{
int retval;
+ if (WARN_ON_ONCE(query_flags & AT_GETATTR_NOSEC))
+ return -EPERM;
+
retval = security_inode_getattr(path);
if (retval)
return retval;
#define AT_HANDLE_FID AT_REMOVEDIR /* file handle is needed to
compare object identity and may not
be usable to open_by_handle_at(2) */
+#if defined(__KERNEL__)
+#define AT_GETATTR_NOSEC 0x80000000
+#endif
#endif /* _UAPI_LINUX_FCNTL_H */