[RFC PATCH v1 02/13] exec: add an internal helper for opened executables
From: Li Chen <hidden>
Date: 2026-05-28 09:54:20
Also in:
linux-arch, linux-doc, linux-fsdevel, linux-kselftest, linux-mm, lkml
Subsystem:
exec & binfmt api, elf, filesystems (vfs and infrastructure), the rest · Maintainers:
Kees Cook, Alexander Viro, Christian Brauner, Linus Torvalds
Split alloc_bprm_file() from alloc_bprm() so internal callers can build a linux_binprm from an executable file that they already opened. Add kernel_execveat_file() for in-kernel users that need to execute an opened file while still using the normal execve credential, LSM, and binary-format path. Signed-off-by: Li Chen <redacted> --- fs/exec.c | 78 +++++++++++++++++++++++++++++++++++------ include/linux/binfmts.h | 4 +++ 2 files changed, 71 insertions(+), 11 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 53f7b18d2b1ea..5b91a9b208a77 100644
--- a/fs/exec.c
+++ b/fs/exec.c@@ -1392,16 +1392,13 @@ static void free_bprm(struct linux_binprm *bprm) kfree(bprm); } -static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int flags) +static struct linux_binprm *alloc_bprm_file(struct file *file, + struct filename *filename, + int fd, int flags) { struct linux_binprm *bprm; - struct file *file; int retval = -ENOMEM; - file = do_open_execat(fd, filename, flags); - if (IS_ERR(file)) - return ERR_CAST(file); - bprm = kzalloc_obj(*bprm); if (!bprm) { do_close_execat(file);
@@ -1463,6 +1460,17 @@ static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int fl return ERR_PTR(retval); } +static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int flags) +{ + struct file *file; + + file = do_open_execat(fd, filename, flags); + if (IS_ERR(file)) + return ERR_CAST(file); + + return alloc_bprm_file(file, filename, fd, flags); +} + DEFINE_CLASS(bprm, struct linux_binprm *, if (!IS_ERR(_T)) free_bprm(_T), alloc_bprm(fd, name, flags), int fd, struct filename *name, int flags)
@@ -1901,6 +1909,59 @@ int kernel_execve(const char *kernel_filename, return bprm_execve(bprm); } +static inline struct user_arg_ptr native_arg(const char __user *const __user *p) +{ + return (struct user_arg_ptr){.ptr.native = p}; +} + +static int do_execveat_file_common(struct file *file, struct filename *filename, + struct user_arg_ptr argv, + struct user_arg_ptr envp, int flags) +{ + struct linux_binprm *bprm; + struct file *exec_file; + int retval; + + if (flags & ~AT_EMPTY_PATH) + return -EINVAL; + + if ((current->flags & PF_NPROC_EXCEEDED) && + is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) + return -EAGAIN; + + current->flags &= ~PF_NPROC_EXCEEDED; + + retval = exe_file_deny_write_access(file); + if (retval) + return retval; + exec_file = get_file(file); + + bprm = alloc_bprm_file(exec_file, filename, AT_FDCWD, flags); + if (IS_ERR(bprm)) + return PTR_ERR(bprm); + + retval = do_execveat_common_bprm(bprm, argv, envp); + free_bprm(bprm); + return retval; +} + +int kernel_execveat_file(struct file *file, const char *filename, + const void __user *argv, + const void __user *envp, + int flags) +{ + const char __user *const __user *user_argv; + const char __user *const __user *user_envp; + + CLASS(filename_kernel, name)(filename); + + user_argv = (const char __user *const __user *)argv; + user_envp = (const char __user *const __user *)envp; + + return do_execveat_file_common(file, name, native_arg(user_argv), + native_arg(user_envp), flags); +} + void set_binfmt(struct linux_binfmt *new) { struct mm_struct *mm = current->mm;
@@ -1925,11 +1986,6 @@ void set_dumpable(struct mm_struct *mm, int value) __mm_flags_set_mask_dumpable(mm, value); } -static inline struct user_arg_ptr native_arg(const char __user *const __user *p) -{ - return (struct user_arg_ptr){.ptr.native = p}; -} - SYSCALL_DEFINE3(execve, const char __user *, filename, const char __user *const __user *, argv,
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 65abd5ab8836c..c0715678c9a06 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h@@ -141,6 +141,10 @@ extern int transfer_args_to_stack(struct linux_binprm *bprm, unsigned long *sp_location); extern int bprm_change_interp(const char *interp, struct linux_binprm *bprm); int copy_string_kernel(const char *arg, struct linux_binprm *bprm); +int kernel_execveat_file(struct file *file, const char *filename, + const void __user *argv, + const void __user *envp, + int flags); extern void set_binfmt(struct linux_binfmt *new); extern ssize_t read_code(struct file *, unsigned long, loff_t, size_t);
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2.52.0