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Message-ID: <20241219204143.74736-1-hamzamahfooz@linux.microsoft.com>
Date: Thu, 19 Dec 2024 15:41:41 -0500
From: Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>
To: linux-security-module@...r.kernel.org,
io-uring@...r.kernel.org
Cc: Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>,
Paul Moore <paul@...l-moore.com>,
Jens Axboe <axboe@...nel.dk>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Pavel Begunkov <asml.silence@...il.com>,
Stephen Smalley <stephen.smalley.work@...il.com>,
Ondrej Mosnacek <omosnace@...hat.com>,
Thiébaud Weksteen <tweek@...gle.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Bram Bonné <brambonne@...gle.com>,
linux-kernel@...r.kernel.org,
selinux@...r.kernel.org
Subject: [PATCH] lsm,io_uring: add LSM hooks for io_uring_setup()
It is desirable to allow LSM to configure accessibility to io_uring. So,
add an LSM for io_uring_allowed() to guard access to io_uring.
Cc: Paul Moore <paul@...l-moore.com>
Cc: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>
---
include/linux/lsm_hook_defs.h | 1 +
include/linux/security.h | 5 +++++
io_uring/io_uring.c | 21 ++++++++++++++-------
security/security.c | 12 ++++++++++++
security/selinux/hooks.c | 14 ++++++++++++++
security/selinux/include/classmap.h | 2 +-
6 files changed, 47 insertions(+), 8 deletions(-)
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index eb2937599cb0..ee45229418dd 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -456,6 +456,7 @@ LSM_HOOK(int, 0, perf_event_write, struct perf_event *event)
LSM_HOOK(int, 0, uring_override_creds, const struct cred *new)
LSM_HOOK(int, 0, uring_sqpoll, void)
LSM_HOOK(int, 0, uring_cmd, struct io_uring_cmd *ioucmd)
+LSM_HOOK(int, 0, uring_allowed, void)
#endif /* CONFIG_IO_URING */
LSM_HOOK(void, LSM_RET_VOID, initramfs_populated, void)
diff --git a/include/linux/security.h b/include/linux/security.h
index cbdba435b798..0a5e897289e8 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -2351,6 +2351,7 @@ static inline int security_perf_event_write(struct perf_event *event)
extern int security_uring_override_creds(const struct cred *new);
extern int security_uring_sqpoll(void);
extern int security_uring_cmd(struct io_uring_cmd *ioucmd);
+extern int security_uring_allowed(void);
#else
static inline int security_uring_override_creds(const struct cred *new)
{
@@ -2364,6 +2365,10 @@ static inline int security_uring_cmd(struct io_uring_cmd *ioucmd)
{
return 0;
}
+extern int security_uring_allowed(void)
+{
+ return 0;
+}
#endif /* CONFIG_SECURITY */
#endif /* CONFIG_IO_URING */
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 06ff41484e29..0922bb0724c0 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3806,29 +3806,36 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
return io_uring_create(entries, &p, params);
}
-static inline bool io_uring_allowed(void)
+static inline int io_uring_allowed(void)
{
int disabled = READ_ONCE(sysctl_io_uring_disabled);
kgid_t io_uring_group;
if (disabled == 2)
- return false;
+ return -EPERM;
if (disabled == 0 || capable(CAP_SYS_ADMIN))
- return true;
+ goto allowed_lsm;
io_uring_group = make_kgid(&init_user_ns, sysctl_io_uring_group);
if (!gid_valid(io_uring_group))
- return false;
+ return -EPERM;
+
+ if (!in_group_p(io_uring_group))
+ return -EPERM;
- return in_group_p(io_uring_group);
+allowed_lsm:
+ return security_uring_allowed();
}
SYSCALL_DEFINE2(io_uring_setup, u32, entries,
struct io_uring_params __user *, params)
{
- if (!io_uring_allowed())
- return -EPERM;
+ int ret;
+
+ ret = io_uring_allowed();
+ if (ret)
+ return ret;
return io_uring_setup(entries, params);
}
diff --git a/security/security.c b/security/security.c
index 09664e09fec9..e4d532e4ead4 100644
--- a/security/security.c
+++ b/security/security.c
@@ -5996,6 +5996,18 @@ int security_uring_cmd(struct io_uring_cmd *ioucmd)
{
return call_int_hook(uring_cmd, ioucmd);
}
+
+/**
+ * security_uring_allowed() - Check if io_uring_setup() is allowed
+ *
+ * Check whether the current task is allowed to call io_uring_setup().
+ *
+ * Return: Returns 0 if permission is granted.
+ */
+int security_uring_allowed(void)
+{
+ return call_int_hook(uring_allowed);
+}
#endif /* CONFIG_IO_URING */
/**
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 366c87a40bd1..b4e298c51c16 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -7117,6 +7117,19 @@ static int selinux_uring_cmd(struct io_uring_cmd *ioucmd)
return avc_has_perm(current_sid(), isec->sid,
SECCLASS_IO_URING, IO_URING__CMD, &ad);
}
+
+/**
+ * selinux_uring_allowed - check if io_uring_setup() can be called
+ *
+ * Check to see if the current task is allowed to call io_uring_setup().
+ */
+static int selinux_uring_allowed(void)
+{
+ u32 sid = current_sid();
+
+ return avc_has_perm(sid, sid, SECCLASS_IO_URING, IO_URING__ALLOWED,
+ NULL);
+}
#endif /* CONFIG_IO_URING */
static const struct lsm_id selinux_lsmid = {
@@ -7370,6 +7383,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
LSM_HOOK_INIT(uring_override_creds, selinux_uring_override_creds),
LSM_HOOK_INIT(uring_sqpoll, selinux_uring_sqpoll),
LSM_HOOK_INIT(uring_cmd, selinux_uring_cmd),
+ LSM_HOOK_INIT(uring_allowed, selinux_uring_allowed),
#endif
/*
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 2bc20135324a..5ae222f7e543 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -177,7 +177,7 @@ const struct security_class_mapping secclass_map[] = {
{ "perf_event",
{ "open", "cpu", "kernel", "tracepoint", "read", "write", NULL } },
{ "anon_inode", { COMMON_FILE_PERMS, NULL } },
- { "io_uring", { "override_creds", "sqpoll", "cmd", NULL } },
+ { "io_uring", { "override_creds", "sqpoll", "cmd", "allowed", NULL } },
{ "user_namespace", { "create", NULL } },
{ NULL }
};
--
2.47.1
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