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Message-ID: <87o8qkzrxp.fsf_-_@x220.int.ebiederm.org>
Date: Mon, 18 May 2020 19:31:14 -0500
From: ebiederm@...ssion.com (Eric W. Biederman)
To: <linux-kernel@...r.kernel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Oleg Nesterov <oleg@...hat.com>, Jann Horn <jannh@...gle.com>,
Kees Cook <keescook@...omium.org>,
Greg Ungerer <gerg@...ux-m68k.org>,
Rob Landley <rob@...dley.net>,
Bernd Edlinger <bernd.edlinger@...mail.de>,
<linux-fsdevel@...r.kernel.org>, Al Viro <viro@...IV.linux.org.uk>,
Alexey Dobriyan <adobriyan@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Casey Schaufler <casey@...aufler-ca.com>,
linux-security-module@...r.kernel.org,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Andy Lutomirski <luto@...capital.net>
Subject: [PATCH v2 3/8] exec: Convert security_bprm_set_creds into security_bprm_repopulate_creds
Rename bprm->cap_elevated to bprm->active_secureexec and initialize it
in prepare_binprm instead of in cap_bprm_set_creds. Initializing
bprm->active_secureexec in prepare_binprm allows multiple
implementations of security_bprm_repopulate_creds to play nicely with
each other.
Rename security_bprm_set_creds to security_bprm_reopulate_creds to
emphasize that this path recomputes part of bprm->cred. This
recomputation avoids the time of check vs time of use problems that
are inherent in unix #! interpreters.
In short two renames and a move in the location of initializing
bprm->active_secureexec.
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
fs/exec.c | 8 ++++----
include/linux/binfmts.h | 4 ++--
include/linux/lsm_hook_defs.h | 2 +-
include/linux/lsm_hooks.h | 4 ++--
include/linux/security.h | 8 ++++----
security/commoncap.c | 9 ++++-----
security/security.c | 4 ++--
7 files changed, 19 insertions(+), 20 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 9e70da47f8d9..8e3b93d51d31 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1366,7 +1366,7 @@ int begin_new_exec(struct linux_binprm * bprm)
* the final state of setuid/setgid/fscaps can be merged into the
* secureexec flag.
*/
- bprm->secureexec |= bprm->cap_elevated;
+ bprm->secureexec |= bprm->active_secureexec;
if (bprm->secureexec) {
/* Make sure parent cannot signal privileged process. */
@@ -1634,10 +1634,10 @@ int prepare_binprm(struct linux_binprm *bprm)
int retval;
loff_t pos = 0;
+ /* Recompute parts of bprm->cred based on bprm->file */
+ bprm->active_secureexec = 0;
bprm_fill_uid(bprm);
-
- /* fill in binprm security blob */
- retval = security_bprm_set_creds(bprm);
+ retval = security_bprm_repopulate_creds(bprm);
if (retval)
return retval;
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index d1217fcdedea..8605ab4a0f89 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -27,10 +27,10 @@ struct linux_binprm {
unsigned long argmin; /* rlimit marker for copy_strings() */
unsigned int
/*
- * True if most recent call to cap_bprm_set_creds
+ * True if most recent call to security_bprm_set_creds
* resulted in elevated privileges.
*/
- cap_elevated:1,
+ active_secureexec:1,
/*
* Set by bprm_creds_for_exec hook to indicate a
* privilege-gaining exec has happened. Used to set
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index aab0695f41df..1e295ba12c0d 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -50,7 +50,7 @@ LSM_HOOK(int, 0, settime, const struct timespec64 *ts,
const struct timezone *tz)
LSM_HOOK(int, 0, vm_enough_memory, struct mm_struct *mm, long pages)
LSM_HOOK(int, 0, bprm_creds_for_exec, struct linux_binprm *bprm)
-LSM_HOOK(int, 0, bprm_set_creds, struct linux_binprm *bprm)
+LSM_HOOK(int, 0, bprm_repopulate_creds, struct linux_binprm *bprm)
LSM_HOOK(int, 0, bprm_check_security, struct linux_binprm *bprm)
LSM_HOOK(void, LSM_RET_VOID, bprm_committing_creds, struct linux_binprm *bprm)
LSM_HOOK(void, LSM_RET_VOID, bprm_committed_creds, struct linux_binprm *bprm)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index c719af37df20..d618ecc4d660 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -44,7 +44,7 @@
* request libc enable secure mode.
* @bprm contains the linux_binprm structure.
* Return 0 if the hook is successful and permission is granted.
- * @bprm_set_creds:
+ * @bprm_repopulate_creds:
* Assuming that the relevant bits of @bprm->cred->security have been
* previously set, examine @bprm->file and regenerate them. This is
* so that the credentials derived from the interpreter the code is
@@ -53,7 +53,7 @@
* reopen script, and may end up opening something completely different.
* This hook may also optionally check permissions (e.g. for
* transitions between security domains).
- * The hook must set @bprm->cap_elevated to 1 if AT_SECURE should be set to
+ * The hook must set @bprm->active_secureexec to 1 if AT_SECURE should be set to
* request libc enable secure mode.
* @bprm contains the linux_binprm structure.
* Return 0 if the hook is successful and permission is granted.
diff --git a/include/linux/security.h b/include/linux/security.h
index 1bd7a6582775..d23f078eb589 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -140,7 +140,7 @@ extern int cap_capset(struct cred *new, const struct cred *old,
const kernel_cap_t *effective,
const kernel_cap_t *inheritable,
const kernel_cap_t *permitted);
-extern int cap_bprm_set_creds(struct linux_binprm *bprm);
+extern int cap_bprm_repopulate_creds(struct linux_binprm *bprm);
extern int cap_inode_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags);
extern int cap_inode_removexattr(struct dentry *dentry, const char *name);
@@ -277,7 +277,7 @@ int security_syslog(int type);
int security_settime64(const struct timespec64 *ts, const struct timezone *tz);
int security_vm_enough_memory_mm(struct mm_struct *mm, long pages);
int security_bprm_creds_for_exec(struct linux_binprm *bprm);
-int security_bprm_set_creds(struct linux_binprm *bprm);
+int security_bprm_repopulate_creds(struct linux_binprm *bprm);
int security_bprm_check(struct linux_binprm *bprm);
void security_bprm_committing_creds(struct linux_binprm *bprm);
void security_bprm_committed_creds(struct linux_binprm *bprm);
@@ -575,9 +575,9 @@ static inline int security_bprm_creds_for_exec(struct linux_binprm *bprm)
return 0;
}
-static inline int security_bprm_set_creds(struct linux_binprm *bprm)
+static inline int security_bprm_repopulate_creds(struct linux_binprm *bprm)
{
- return cap_bprm_set_creds(bprm);
+ return cap_bprm_repopluate_creds(bprm);
}
static inline int security_bprm_check(struct linux_binprm *bprm)
diff --git a/security/commoncap.c b/security/commoncap.c
index f4ee0ae106b2..045b5b80ea40 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -797,14 +797,14 @@ static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
}
/**
- * cap_bprm_set_creds - Set up the proposed credentials for execve().
+ * cap_bprm_repopulate_creds - Set up the proposed credentials for execve().
* @bprm: The execution parameters, including the proposed creds
*
* Set up the proposed credentials for a new execution context being
* constructed by execve(). The proposed creds in @bprm->cred is altered,
* which won't take effect immediately. Returns 0 if successful, -ve on error.
*/
-int cap_bprm_set_creds(struct linux_binprm *bprm)
+int cap_bprm_repopulate_creds(struct linux_binprm *bprm)
{
const struct cred *old = current_cred();
struct cred *new = bprm->cred;
@@ -884,12 +884,11 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
return -EPERM;
/* Check for privilege-elevated exec. */
- bprm->cap_elevated = 0;
if (is_setid ||
(!__is_real(root_uid, new) &&
(effective ||
__cap_grew(permitted, ambient, new))))
- bprm->cap_elevated = 1;
+ bprm->active_secureexec = 1;
return 0;
}
@@ -1346,7 +1345,7 @@ static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
LSM_HOOK_INIT(capget, cap_capget),
LSM_HOOK_INIT(capset, cap_capset),
- LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds),
+ LSM_HOOK_INIT(bprm_repopulate_creds, cap_bprm_repopulate_creds),
LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
diff --git a/security/security.c b/security/security.c
index 4ee76a729f73..b890b7e2a765 100644
--- a/security/security.c
+++ b/security/security.c
@@ -828,9 +828,9 @@ int security_bprm_creds_for_exec(struct linux_binprm *bprm)
return call_int_hook(bprm_creds_for_exec, 0, bprm);
}
-int security_bprm_set_creds(struct linux_binprm *bprm)
+int security_bprm_repopulate_creds(struct linux_binprm *bprm)
{
- return call_int_hook(bprm_set_creds, 0, bprm);
+ return call_int_hook(bprm_repopulate_creds, 0, bprm);
}
int security_bprm_check(struct linux_binprm *bprm)
--
2.25.0
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