68 lines
2.2 KiB
Diff
68 lines
2.2 KiB
Diff
From: Anthony G. Basile <blueness@gentoo.org>
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This patch adds support for a restricted user-controlled namespace on
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tmpfs filesystem used to house PaX flags. The namespace must be of the
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form user.pax.* and its value cannot exceed a size of 8 bytes.
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This is needed even on all Gentoo systems so that XATTR_PAX flags
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are preserved for users who might build packages using portage on
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a tmpfs system with a non-hardened kernel and then switch to a
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hardened kernel with XATTR_PAX enabled.
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The namespace is added to any user with Extended Attribute support
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enabled for tmpfs. Users who do not enable xattrs will not have
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the XATTR_PAX flags preserved.
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diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h
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index 1590c49..5eab462 100644
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--- a/include/uapi/linux/xattr.h
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+++ b/include/uapi/linux/xattr.h
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@@ -73,5 +73,9 @@
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#define XATTR_POSIX_ACL_DEFAULT "posix_acl_default"
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#define XATTR_NAME_POSIX_ACL_DEFAULT XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_DEFAULT
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+/* User namespace */
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+#define XATTR_PAX_PREFIX XATTR_USER_PREFIX "pax."
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+#define XATTR_PAX_FLAGS_SUFFIX "flags"
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+#define XATTR_NAME_PAX_FLAGS XATTR_PAX_PREFIX XATTR_PAX_FLAGS_SUFFIX
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#endif /* _UAPI_LINUX_XATTR_H */
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--- a/mm/shmem.c 2020-05-04 15:30:27.042035334 -0400
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+++ b/mm/shmem.c 2020-05-04 15:34:57.013881725 -0400
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@@ -3238,6 +3238,14 @@ static int shmem_xattr_handler_set(const
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struct shmem_inode_info *info = SHMEM_I(inode);
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name = xattr_full_name(handler, name);
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+
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+ if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
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+ if (strcmp(name, XATTR_NAME_PAX_FLAGS))
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+ return -EOPNOTSUPP;
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+ if (size > 8)
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+ return -EINVAL;
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+ }
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+
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return simple_xattr_set(&info->xattrs, name, value, size, flags, NULL);
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}
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@@ -3253,6 +3261,12 @@ static const struct xattr_handler shmem_
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.set = shmem_xattr_handler_set,
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};
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+static const struct xattr_handler shmem_user_xattr_handler = {
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+ .prefix = XATTR_USER_PREFIX,
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+ .get = shmem_xattr_handler_get,
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+ .set = shmem_xattr_handler_set,
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+};
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+
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static const struct xattr_handler *shmem_xattr_handlers[] = {
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#ifdef CONFIG_TMPFS_POSIX_ACL
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&posix_acl_access_xattr_handler,
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@@ -3260,6 +3274,7 @@ static const struct xattr_handler *shmem
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#endif
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&shmem_security_xattr_handler,
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&shmem_trusted_xattr_handler,
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+ &shmem_user_xattr_handler,
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NULL
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};
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