The patch titled
Subject: syscalls: implement execveat() system call
has been removed from the -mm tree. Its filename was
syscalls-implement-execveat-system-call.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: David Drysdale <drysdale@xxxxxxxxxx>
Subject: syscalls: implement execveat() system call
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@xxxxxxxxxx>
Cc: Meredydd Luff <meredydd@xxxxxxxxxxxxxxx>
Cc: Shuah Khan <shuah.kh@xxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Rich Felker <dalias@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/binfmt_em86.c | 4
fs/binfmt_misc.c | 4
fs/binfmt_script.c | 10 ++
fs/exec.c | 113 ++++++++++++++++++++++++----
fs/namei.c | 2
include/linux/binfmts.h | 4
include/linux/compat.h | 3
include/linux/fs.h | 1
include/linux/sched.h | 4
include/linux/syscalls.h | 5 +
include/uapi/asm-generic/unistd.h | 4
kernel/sys_ni.c | 3
lib/audit.c | 3
13 files changed, 145 insertions(+), 15 deletions(-)
diff -puN fs/binfmt_em86.c~syscalls-implement-execveat-system-call fs/binfmt_em86.c
--- a/fs/binfmt_em86.c~syscalls-implement-execveat-system-call
+++ a/fs/binfmt_em86.c
@@ -42,6 +42,10 @@ static int load_em86(struct linux_binprm
return -ENOEXEC;
}
+ /* Need to be able to load the file after exec */
+ if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
+ return -ENOENT;
+
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;
diff -puN fs/binfmt_misc.c~syscalls-implement-execveat-system-call fs/binfmt_misc.c
--- a/fs/binfmt_misc.c~syscalls-implement-execveat-system-call
+++ a/fs/binfmt_misc.c
@@ -144,6 +144,10 @@ static int load_misc_binary(struct linux
if (!fmt)
goto ret;
+ /* Need to be able to load the file after exec */
+ if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
+ return -ENOENT;
+
if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
retval = remove_arg_zero(bprm);
if (retval)
diff -puN fs/binfmt_script.c~syscalls-implement-execveat-system-call fs/binfmt_script.c
--- a/fs/binfmt_script.c~syscalls-implement-execveat-system-call
+++ a/fs/binfmt_script.c
@@ -24,6 +24,16 @@ static int load_script(struct linux_binp
if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
return -ENOEXEC;
+
+ /*
+ * If the script filename will be inaccessible after exec, typically
+ * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give
+ * up now (on the assumption that the interpreter will want to load
+ * this file).
+ */
+ if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
+ return -ENOENT;
+
/*
* This section does the #! interpretation.
* Sorta complicated, but hopefully it will work. -TYT
diff -puN fs/exec.c~syscalls-implement-execveat-system-call fs/exec.c
--- a/fs/exec.c~syscalls-implement-execveat-system-call
+++ a/fs/exec.c
@@ -748,18 +748,25 @@ EXPORT_SYMBOL(setup_arg_pages);
#endif /* CONFIG_MMU */
-static struct file *do_open_exec(struct filename *name)
+static struct file *do_open_execat(int fd, struct filename *name, int flags)
{
struct file *file;
int err;
- static const struct open_flags open_exec_flags = {
+ struct open_flags open_exec_flags = {
.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
.acc_mode = MAY_EXEC | MAY_OPEN,
.intent = LOOKUP_OPEN,
.lookup_flags = LOOKUP_FOLLOW,
};
- file = do_filp_open(AT_FDCWD, name, &open_exec_flags);
+ if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
+ return ERR_PTR(-EINVAL);
+ if (flags & AT_SYMLINK_NOFOLLOW)
+ open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
+ if (flags & AT_EMPTY_PATH)
+ open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
+
+ file = do_filp_open(fd, name, &open_exec_flags);
if (IS_ERR(file))
goto out;
@@ -770,12 +777,13 @@ static struct file *do_open_exec(struct
if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
goto exit;
- fsnotify_open(file);
-
err = deny_write_access(file);
if (err)
goto exit;
+ if (name->name[0] != '\0')
+ fsnotify_open(file);
+
out:
return file;
@@ -787,7 +795,7 @@ exit:
struct file *open_exec(const char *name)
{
struct filename tmp = { .name = name };
- return do_open_exec(&tmp);
+ return do_open_execat(AT_FDCWD, &tmp, 0);
}
EXPORT_SYMBOL(open_exec);
@@ -1428,10 +1436,12 @@ static int exec_binprm(struct linux_binp
/*
* sys_execve() executes a new program.
*/
-static int do_execve_common(struct filename *filename,
- struct user_arg_ptr argv,
- struct user_arg_ptr envp)
+static int do_execveat_common(int fd, struct filename *filename,
+ struct user_arg_ptr argv,
+ struct user_arg_ptr envp,
+ int flags)
{
+ char *pathbuf = NULL;
struct linux_binprm *bprm;
struct file *file;
struct files_struct *displaced;
@@ -1472,7 +1482,7 @@ static int do_execve_common(struct filen
check_unsafe_exec(bprm);
current->in_execve = 1;
- file = do_open_exec(filename);
+ file = do_open_execat(fd, filename, flags);
retval = PTR_ERR(file);
if (IS_ERR(file))
goto out_unmark;
@@ -1480,7 +1490,28 @@ static int do_execve_common(struct filen
sched_exec();
bprm->file = file;
- bprm->filename = bprm->interp = filename->name;
+ if (fd == AT_FDCWD || filename->name[0] == '/') {
+ bprm->filename = filename->name;
+ } else {
+ if (filename->name[0] == '\0')
+ pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd);
+ else
+ pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s",
+ fd, filename->name);
+ if (!pathbuf) {
+ retval = -ENOMEM;
+ goto out_unmark;
+ }
+ /*
+ * Record that a name derived from an O_CLOEXEC fd will be
+ * inaccessible after exec. Relies on having exclusive access to
+ * current->files (due to unshare_files above).
+ */
+ if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
+ bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
+ bprm->filename = pathbuf;
+ }
+ bprm->interp = bprm->filename;
retval = bprm_mm_init(bprm);
if (retval)
@@ -1521,6 +1552,7 @@ static int do_execve_common(struct filen
acct_update_integrals(current);
task_numa_free(current);
free_bprm(bprm);
+ kfree(pathbuf);
putname(filename);
if (displaced)
put_files_struct(displaced);
@@ -1538,6 +1570,7 @@ out_unmark:
out_free:
free_bprm(bprm);
+ kfree(pathbuf);
out_files:
if (displaced)
@@ -1553,7 +1586,18 @@ int do_execve(struct filename *filename,
{
struct user_arg_ptr argv = { .ptr.native = __argv };
struct user_arg_ptr envp = { .ptr.native = __envp };
- return do_execve_common(filename, argv, 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)
+{
+ 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
@@ -1569,7 +1613,23 @@ static int compat_do_execve(struct filen
.is_compat = true,
.ptr.compat = __envp,
};
- return do_execve_common(filename, argv, 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);
}
#endif
@@ -1609,6 +1669,20 @@ SYSCALL_DEFINE3(execve,
{
return do_execve(getname(filename), argv, envp);
}
+
+SYSCALL_DEFINE5(execveat,
+ int, fd, const char __user *, filename,
+ const char __user *const __user *, argv,
+ const char __user *const __user *, envp,
+ int, flags)
+{
+ int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
+
+ return do_execveat(fd,
+ getname_flags(filename, lookup_flags, NULL),
+ argv, envp, flags);
+}
+
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
const compat_uptr_t __user *, argv,
@@ -1616,4 +1690,17 @@ COMPAT_SYSCALL_DEFINE3(execve, const cha
{
return compat_do_execve(getname(filename), argv, envp);
}
+
+COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
+ const char __user *, filename,
+ const compat_uptr_t __user *, argv,
+ const compat_uptr_t __user *, envp,
+ int, flags)
+{
+ int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
+
+ return compat_do_execveat(fd,
+ getname_flags(filename, lookup_flags, NULL),
+ argv, envp, flags);
+}
#endif
diff -puN fs/namei.c~syscalls-implement-execveat-system-call fs/namei.c
--- a/fs/namei.c~syscalls-implement-execveat-system-call
+++ a/fs/namei.c
@@ -130,7 +130,7 @@ void final_putname(struct filename *name
#define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
-static struct filename *
+struct filename *
getname_flags(const char __user *filename, int flags, int *empty)
{
struct filename *result, *err;
diff -puN include/linux/binfmts.h~syscalls-implement-execveat-system-call include/linux/binfmts.h
--- a/include/linux/binfmts.h~syscalls-implement-execveat-system-call
+++ a/include/linux/binfmts.h
@@ -53,6 +53,10 @@ struct linux_binprm {
#define BINPRM_FLAGS_EXECFD_BIT 1
#define BINPRM_FLAGS_EXECFD (1 << BINPRM_FLAGS_EXECFD_BIT)
+/* filename of the binary will be inaccessible after exec */
+#define BINPRM_FLAGS_PATH_INACCESSIBLE_BIT 2
+#define BINPRM_FLAGS_PATH_INACCESSIBLE (1 << BINPRM_FLAGS_PATH_INACCESSIBLE_BIT)
+
/* Function parameter for binfmt->coredump */
struct coredump_params {
const siginfo_t *siginfo;
diff -puN include/linux/compat.h~syscalls-implement-execveat-system-call include/linux/compat.h
--- a/include/linux/compat.h~syscalls-implement-execveat-system-call
+++ a/include/linux/compat.h
@@ -357,6 +357,9 @@ asmlinkage long compat_sys_lseek(unsigne
asmlinkage long compat_sys_execve(const char __user *filename, const compat_uptr_t __user *argv,
const compat_uptr_t __user *envp);
+asmlinkage long compat_sys_execveat(int dfd, const char __user *filename,
+ const compat_uptr_t __user *argv,
+ const compat_uptr_t __user *envp, int flags);
asmlinkage long compat_sys_select(int n, compat_ulong_t __user *inp,
compat_ulong_t __user *outp, compat_ulong_t __user *exp,
diff -puN include/linux/fs.h~syscalls-implement-execveat-system-call include/linux/fs.h
--- a/include/linux/fs.h~syscalls-implement-execveat-system-call
+++ a/include/linux/fs.h
@@ -2096,6 +2096,7 @@ extern int vfs_open(const struct path *,
extern struct file * dentry_open(const struct path *, int, const struct cred *);
extern int filp_close(struct file *, fl_owner_t id);
+extern struct filename *getname_flags(const char __user *, int, int *);
extern struct filename *getname(const char __user *);
extern struct filename *getname_kernel(const char *);
diff -puN include/linux/sched.h~syscalls-implement-execveat-system-call include/linux/sched.h
--- a/include/linux/sched.h~syscalls-implement-execveat-system-call
+++ a/include/linux/sched.h
@@ -2485,6 +2485,10 @@ extern void do_group_exit(int);
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);
extern long do_fork(unsigned long, unsigned long, unsigned long, int __user *, int __user *);
struct task_struct *fork_idle(int);
extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
diff -puN include/linux/syscalls.h~syscalls-implement-execveat-system-call include/linux/syscalls.h
--- a/include/linux/syscalls.h~syscalls-implement-execveat-system-call
+++ a/include/linux/syscalls.h
@@ -877,4 +877,9 @@ asmlinkage long sys_seccomp(unsigned int
asmlinkage long sys_getrandom(char __user *buf, size_t count,
unsigned int flags);
asmlinkage long sys_bpf(int cmd, union bpf_attr *attr, unsigned int size);
+
+asmlinkage long sys_execveat(int dfd, const char __user *filename,
+ const char __user *const __user *argv,
+ const char __user *const __user *envp, int flags);
+
#endif
diff -puN include/uapi/asm-generic/unistd.h~syscalls-implement-execveat-system-call include/uapi/asm-generic/unistd.h
--- a/include/uapi/asm-generic/unistd.h~syscalls-implement-execveat-system-call
+++ a/include/uapi/asm-generic/unistd.h
@@ -707,9 +707,11 @@ __SYSCALL(__NR_getrandom, sys_getrandom)
__SYSCALL(__NR_memfd_create, sys_memfd_create)
#define __NR_bpf 280
__SYSCALL(__NR_bpf, sys_bpf)
+#define __NR_execveat 281
+__SC_COMP(__NR_execveat, sys_execveat, compat_sys_execveat)
#undef __NR_syscalls
-#define __NR_syscalls 281
+#define __NR_syscalls 282
/*
* All syscalls below here should go away really,
diff -puN kernel/sys_ni.c~syscalls-implement-execveat-system-call kernel/sys_ni.c
--- a/kernel/sys_ni.c~syscalls-implement-execveat-system-call
+++ a/kernel/sys_ni.c
@@ -226,3 +226,6 @@ cond_syscall(sys_seccomp);
/* access BPF programs and maps */
cond_syscall(sys_bpf);
+
+/* execveat */
+cond_syscall(sys_execveat);
diff -puN lib/audit.c~syscalls-implement-execveat-system-call lib/audit.c
--- a/lib/audit.c~syscalls-implement-execveat-system-call
+++ a/lib/audit.c
@@ -54,6 +54,9 @@ int audit_classify_syscall(int abi, unsi
case __NR_socketcall:
return 4;
#endif
+#ifdef __NR_execveat
+ case __NR_execveat:
+#endif
case __NR_execve:
return 5;
default:
_
Patches currently in -mm which might be from drysdale@xxxxxxxxxx are
origin.patch
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