[PATCH 1/6] exec: cleanup the execve wrappers

Christoph Hellwig
2020-06-15T13:00:57Z

Remove a whole bunch of wrappers that eventually all call
__do_execve_file, and consolidate the execvce helpers to:

(1) __do_execveat, which is the lowest level helper implementing the
actual functionality
(2) do_execvat, which is used by all callers that want native
pointers
(3) do_compat_execve, which is used by all compat syscalls

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/exec.c | 98 +++++++++++------------------------------
include/linux/binfmts.h | 12 ++---
init/main.c | 7 +--
kernel/umh.c | 16 +++----
4 files changed, 41 insertions(+), 92 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index e6e8a9a7032784..354fdaa536ae7d 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1815,10 +1815,7 @@ static int exec_binprm(struct linux_binprm *bprm)
return 0;
}

-/*
- * sys_execve() executes a new program.
- */
-static int __do_execve_file(int fd, struct filename *filename,
+static int __do_execveat(int fd, struct filename *filename,
struct user_arg_ptr argv,
struct user_arg_ptr envp,
int flags, struct file *file)
@@ -1972,74 +1969,16 @@ static int __do_execve_file(int fd, struct filename *filename,
return retval;
}

-static int do_execveat_common(int fd, struct filename *filename,
- struct user_arg_ptr argv,
- struct user_arg_ptr envp,
- int flags)
-{
- return __do_execve_file(fd, filename, argv, envp, flags, NULL);
-}
-
-int do_execve_file(struct file *file, void *__argv, void *__envp)
-{
- struct user_arg_ptr argv = { .ptr.native = __argv };
- struct user_arg_ptr envp = { .ptr.native = __envp };
-
- return __do_execve_file(AT_FDCWD, NULL, argv, envp, 0, file);
-}
-
-int do_execve(struct filename *filename,
- const char __user *const __user *__argv,
- const char __user *const __user *__envp)
-{
- struct user_arg_ptr argv = { .ptr.native = __argv };
- struct user_arg_ptr envp = { .ptr.native = __envp };
- return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
-}
-
int do_execveat(int fd, struct filename *filename,
const char __user *const __user *__argv,
const char __user *const __user *__envp,
- int flags)
+ int flags, struct file *file)
{
struct user_arg_ptr argv = { .ptr.native = __argv };
struct user_arg_ptr envp = { .ptr.native = __envp };

- return do_execveat_common(fd, filename, argv, envp, flags);
-}
-
-#ifdef CONFIG_COMPAT
-static int compat_do_execve(struct filename *filename,
- const compat_uptr_t __user *__argv,
- const compat_uptr_t __user *__envp)
-{
- struct user_arg_ptr argv = {
- .is_compat = true,
- .ptr.compat = __argv,
- };
- struct user_arg_ptr envp = {
- .is_compat = true,
- .ptr.compat = __envp,
- };
- return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
-}
-
-static int compat_do_execveat(int fd, struct filename *filename,
- const compat_uptr_t __user *__argv,
- const compat_uptr_t __user *__envp,
- int flags)
-{
- struct user_arg_ptr argv = {
- .is_compat = true,
- .ptr.compat = __argv,
- };
- struct user_arg_ptr envp = {
- .is_compat = true,
- .ptr.compat = __envp,
- };
- return do_execveat_common(fd, filename, argv, envp, flags);
+ return __do_execveat(fd, filename, argv, envp, flags, file);
}
-#endif

void set_binfmt(struct linux_binfmt *new)
{
@@ -2070,7 +2009,7 @@ SYSCALL_DEFINE3(execve,
const char __user *const __user *, argv,
const char __user *const __user *, envp)
{
- return do_execve(getname(filename), argv, envp);
+ return do_execveat(AT_FDCWD, getname(filename), argv, envp, 0, NULL);
}

SYSCALL_DEFINE5(execveat,
@@ -2080,18 +2019,34 @@ SYSCALL_DEFINE5(execveat,
int, flags)
{
int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
+ struct filename *name = getname_flags(filename, lookup_flags, NULL);

- return do_execveat(fd,
- getname_flags(filename, lookup_flags, NULL),
- argv, envp, flags);
+ return do_execveat(fd, name, argv, envp, flags, NULL);
}

#ifdef CONFIG_COMPAT
+static int do_compat_execve(int fd, struct filename *filename,
+ const compat_uptr_t __user *__argv,
+ const compat_uptr_t __user *__envp,
+ int flags)
+{
+ struct user_arg_ptr argv = {
+ .is_compat = true,
+ .ptr.compat = __argv,
+ };
+ struct user_arg_ptr envp = {
+ .is_compat = true,
+ .ptr.compat = __envp,
+ };
+
+ return __do_execveat(fd, filename, argv, envp, flags, NULL);
+}
+
COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
const compat_uptr_t __user *, argv,
const compat_uptr_t __user *, envp)
{
- return compat_do_execve(getname(filename), argv, envp);
+ return do_compat_execve(AT_FDCWD, getname(filename), argv, envp, 0);
}

COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
@@ -2101,9 +2056,8 @@ COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
int, flags)
{
int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
+ struct filename *name = getname_flags(filename, lookup_flags, NULL);

- return compat_do_execveat(fd,
- getname_flags(filename, lookup_flags, NULL),
- argv, envp, flags);
+ return do_compat_execve(fd, name, argv, envp, flags);
}
#endif
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 4a20b7517dd036..bed702e4b1fbd9 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -134,13 +134,9 @@ int copy_string_kernel(const char *arg, 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);

-extern int do_execve(struct filename *,
- const char __user * const __user *,
- const char __user * const __user *);
-extern int do_execveat(int, struct filename *,
- const char __user * const __user *,
- const char __user * const __user *,
- int);
-int do_execve_file(struct file *file, void *__argv, void *__envp);
+int do_execveat(int fd, struct filename *filename,
+ const char __user *const __user *__argv,
+ const char __user *const __user *__envp,
+ int flags, struct file *file);

#endif /* _LINUX_BINFMTS_H */
diff --git a/init/main.c b/init/main.c
index 0ead83e86b5aa2..838950ea7bca22 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1329,9 +1329,10 @@ static int run_init_process(const char *init_filename)
pr_debug(" with environment:\n");
for (p = envp_init; *p; p++)
pr_debug(" %s\n", *p);
- return do_execve(getname_kernel(init_filename),
- (const char __user *const __user *)argv_init,
- (const char __user *const __user *)envp_init);
+ return do_execveat(AT_FDCWD, getname_kernel(init_filename),
+ (const char __user *const __user *)argv_init,
+ (const char __user *const __user *)envp_init,
+ 0, NULL);
}

static int try_to_run_init_process(const char *init_filename)
diff --git a/kernel/umh.c b/kernel/umh.c
index 79f139a7ca03c6..7aa9a5817582ca 100644
--- a/kernel/umh.c
+++ b/kernel/umh.c
@@ -103,15 +103,13 @@ static int call_usermodehelper_exec_async(void *data)
commit_creds(new);

sub_info->pid = task_pid_nr(current);
- if (sub_info->file) {
- retval = do_execve_file(sub_info->file,
- sub_info->argv, sub_info->envp);
- if (!retval)
- current->flags |= PF_UMH;
- } else
- retval = do_execve(getname_kernel(sub_info->path),
- (const char __user *const __user *)sub_info->argv,
- (const char __user *const __user *)sub_info->envp);
+ retval = do_execveat(AT_FDCWD,
+ sub_info->path ? getname_kernel(sub_info->path) : NULL,
+ (const char __user *const __user *)sub_info->argv,
+ (const char __user *const __user *)sub_info->envp,
+ 0, sub_info->file);
+ if (sub_info->file && !retval)
+ current->flags |= PF_UMH;
out:
sub_info->retval = retval;
/*
--
2.26.2