[PATCH 4/7] exec: Merge install_exec_creds into setup_new_exec

From: Eric W. Biederman
Date: Tue May 05 2020 - 15:47:09 EST


The two functions are now always called one right after the
other so merge them together to make future maintenance easier.

Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
arch/x86/ia32/ia32_aout.c | 1 -
fs/binfmt_aout.c | 1 -
fs/binfmt_elf.c | 1 -
fs/binfmt_elf_fdpic.c | 1 -
fs/binfmt_flat.c | 1 -
fs/exec.c | 56 ++++++++++++++++++---------------------
include/linux/binfmts.h | 1 -
kernel/events/core.c | 2 +-
8 files changed, 27 insertions(+), 37 deletions(-)

diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
index 37b36a8ce5fa..8255fdc3a027 100644
--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -140,7 +140,6 @@ static int load_aout_binary(struct linux_binprm *bprm)
set_personality_ia32(false);

setup_new_exec(bprm);
- install_exec_creds(bprm);

regs->cs = __USER32_CS;
regs->r8 = regs->r9 = regs->r10 = regs->r11 = regs->r12 =
diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
index ace587b66904..c8ba28f285e5 100644
--- a/fs/binfmt_aout.c
+++ b/fs/binfmt_aout.c
@@ -162,7 +162,6 @@ static int load_aout_binary(struct linux_binprm * bprm)
set_personality(PER_LINUX);
#endif
setup_new_exec(bprm);
- install_exec_creds(bprm);

current->mm->end_code = ex.a_text +
(current->mm->start_code = N_TXTADDR(ex));
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 13f25e241ac4..e6b586623035 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -858,7 +858,6 @@ static int load_elf_binary(struct linux_binprm *bprm)
current->flags |= PF_RANDOMIZE;

setup_new_exec(bprm);
- install_exec_creds(bprm);

/* Do this so that we can load the interpreter, if need be. We will
change some of these later */
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 6c94c6d53d97..9a1aa61b4cc3 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -353,7 +353,6 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm)
current->personality |= READ_IMPLIES_EXEC;

setup_new_exec(bprm);
- install_exec_creds(bprm);

set_binfmt(&elf_fdpic_format);

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 1a1d1fcb893f..252878969582 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -541,7 +541,6 @@ static int load_flat_file(struct linux_binprm *bprm,
/* OK, This is the point of no return */
set_personality(PER_LINUX_32BIT);
setup_new_exec(bprm);
- install_exec_creds(bprm);
}

/*
diff --git a/fs/exec.c b/fs/exec.c
index 71de9f57ae09..93e40f865523 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1443,6 +1443,31 @@ void setup_new_exec(struct linux_binprm * bprm)
group */
WRITE_ONCE(current->self_exec_id, current->self_exec_id + 1);
flush_signal_handlers(current, 0);
+
+ /*
+ * install the new credentials for this executable
+ */
+ security_bprm_committing_creds(bprm);
+
+ commit_creds(bprm->cred);
+ bprm->cred = NULL;
+
+ /*
+ * Disable monitoring for regular users
+ * when executing setuid binaries. Must
+ * wait until new credentials are committed
+ * by commit_creds() above
+ */
+ if (get_dumpable(current->mm) != SUID_DUMP_USER)
+ perf_event_exit_task(current);
+ /*
+ * cred_guard_mutex must be held at least to this point to prevent
+ * ptrace_attach() from altering our determination of the task's
+ * credentials; any time after this it may be unlocked.
+ */
+ security_bprm_committed_creds(bprm);
+ mutex_unlock(&current->signal->exec_update_mutex);
+ mutex_unlock(&current->signal->cred_guard_mutex);
}
EXPORT_SYMBOL(setup_new_exec);

@@ -1458,7 +1483,7 @@ EXPORT_SYMBOL(finalize_exec);

/*
* Prepare credentials and lock ->cred_guard_mutex.
- * install_exec_creds() commits the new creds and drops the lock.
+ * setup_new_exec() commits the new creds and drops the lock.
* Or, if exec fails before, free_bprm() should release ->cred and
* and unlock.
*/
@@ -1504,35 +1529,6 @@ int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
}
EXPORT_SYMBOL(bprm_change_interp);

-/*
- * install the new credentials for this executable
- */
-void install_exec_creds(struct linux_binprm *bprm)
-{
- security_bprm_committing_creds(bprm);
-
- commit_creds(bprm->cred);
- bprm->cred = NULL;
-
- /*
- * Disable monitoring for regular users
- * when executing setuid binaries. Must
- * wait until new credentials are committed
- * by commit_creds() above
- */
- if (get_dumpable(current->mm) != SUID_DUMP_USER)
- perf_event_exit_task(current);
- /*
- * cred_guard_mutex must be held at least to this point to prevent
- * ptrace_attach() from altering our determination of the task's
- * credentials; any time after this it may be unlocked.
- */
- security_bprm_committed_creds(bprm);
- mutex_unlock(&current->signal->exec_update_mutex);
- mutex_unlock(&current->signal->cred_guard_mutex);
-}
-EXPORT_SYMBOL(install_exec_creds);
-
/*
* determine how safe it is to execute the proposed program
* - the caller must hold ->cred_guard_mutex to protect against
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 8f479dad7931..2a8fddf3574a 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -145,7 +145,6 @@ extern int transfer_args_to_stack(struct linux_binprm *bprm,
extern int bprm_change_interp(const char *interp, struct linux_binprm *bprm);
extern int copy_strings_kernel(int argc, const char *const *argv,
struct linux_binprm *bprm);
-extern void install_exec_creds(struct linux_binprm *bprm);
extern void set_binfmt(struct linux_binfmt *new);
extern ssize_t read_code(struct file *, unsigned long, loff_t, size_t);

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 633b4ae72ed5..169449b5e56b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -12217,7 +12217,7 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
* When a child task exits, feed back event values to parent events.
*
* Can be called with exec_update_mutex held when called from
- * install_exec_creds().
+ * setup_new_exec().
*/
void perf_event_exit_task(struct task_struct *child)
{
--
2.20.1