David Drysdale <drysdale@xxxxxxxxxx> writes: > Add a new system execveat(2) syscall. 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. > > Only x86-64, i386 and x32 ABIs are supported in this patch. > > Based on patches by Meredydd Luff <meredydd@xxxxxxxxxxxxxxx> > > Signed-off-by: David Drysdale <drysdale@xxxxxxxxxx> > --- > arch/x86/ia32/audit.c | 1 + > arch/x86/ia32/ia32entry.S | 1 + > arch/x86/kernel/audit_64.c | 1 + > arch/x86/kernel/entry_64.S | 28 ++++++++ > arch/x86/syscalls/syscall_32.tbl | 1 + > arch/x86/syscalls/syscall_64.tbl | 2 + > arch/x86/um/sys_call_table_64.c | 1 + > fs/exec.c | 130 ++++++++++++++++++++++++++++++++++---- > fs/namei.c | 2 +- > include/linux/compat.h | 3 + > include/linux/fs.h | 1 + > include/linux/sched.h | 4 ++ > include/linux/syscalls.h | 4 ++ > include/uapi/asm-generic/unistd.h | 4 +- > kernel/sys_ni.c | 3 + > lib/audit.c | 3 + > 16 files changed, 173 insertions(+), 16 deletions(-) > > diff --git a/arch/x86/ia32/audit.c b/arch/x86/ia32/audit.c > index 5d7b381da692..2eccc8932ae6 100644 > --- a/arch/x86/ia32/audit.c > +++ b/arch/x86/ia32/audit.c > @@ -35,6 +35,7 @@ int ia32_classify_syscall(unsigned syscall) > case __NR_socketcall: > return 4; > case __NR_execve: > + case __NR_execveat: > return 5; > default: > return 1; > diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S > index 4299eb05023c..2516c09743e0 100644 > --- a/arch/x86/ia32/ia32entry.S > +++ b/arch/x86/ia32/ia32entry.S > @@ -464,6 +464,7 @@ GLOBAL(\label) > PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn > PTREGSCALL stub32_sigreturn, sys32_sigreturn > PTREGSCALL stub32_execve, compat_sys_execve > + PTREGSCALL stub32_execveat, compat_sys_execveat > PTREGSCALL stub32_fork, sys_fork > PTREGSCALL stub32_vfork, sys_vfork > > diff --git a/arch/x86/kernel/audit_64.c b/arch/x86/kernel/audit_64.c > index 06d3e5a14d9d..f3672508b249 100644 > --- a/arch/x86/kernel/audit_64.c > +++ b/arch/x86/kernel/audit_64.c > @@ -50,6 +50,7 @@ int audit_classify_syscall(int abi, unsigned syscall) > case __NR_openat: > return 3; > case __NR_execve: > + case __NR_execveat: > return 5; > default: > return 0; > diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S > index 2fac1343a90b..00c4526e6ffe 100644 > --- a/arch/x86/kernel/entry_64.S > +++ b/arch/x86/kernel/entry_64.S > @@ -665,6 +665,20 @@ ENTRY(stub_execve) > CFI_ENDPROC > END(stub_execve) > > +ENTRY(stub_execveat) > + CFI_STARTPROC > + addq $8, %rsp > + PARTIAL_FRAME 0 > + SAVE_REST > + FIXUP_TOP_OF_STACK %r11 > + call sys_execveat > + RESTORE_TOP_OF_STACK %r11 > + movq %rax,RAX(%rsp) > + RESTORE_REST > + jmp int_ret_from_sys_call > + CFI_ENDPROC > +END(stub_execveat) > + > /* > * sigreturn is special because it needs to restore all registers on return. > * This cannot be done with SYSRET, so use the IRET return path instead. > @@ -710,6 +724,20 @@ ENTRY(stub_x32_execve) > CFI_ENDPROC > END(stub_x32_execve) > > +ENTRY(stub_x32_execveat) > + CFI_STARTPROC > + addq $8, %rsp > + PARTIAL_FRAME 0 > + SAVE_REST > + FIXUP_TOP_OF_STACK %r11 > + call compat_sys_execveat > + RESTORE_TOP_OF_STACK %r11 > + movq %rax,RAX(%rsp) > + RESTORE_REST > + jmp int_ret_from_sys_call > + CFI_ENDPROC > +END(stub_x32_execveat) > + > #endif > > /* > diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl > index 028b78168d85..2633e3195455 100644 > --- a/arch/x86/syscalls/syscall_32.tbl > +++ b/arch/x86/syscalls/syscall_32.tbl > @@ -363,3 +363,4 @@ > 354 i386 seccomp sys_seccomp > 355 i386 getrandom sys_getrandom > 356 i386 memfd_create sys_memfd_create > +357 i386 execveat sys_execveat stub32_execveat > diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl > index 35dd922727b9..1af5badd159c 100644 > --- a/arch/x86/syscalls/syscall_64.tbl > +++ b/arch/x86/syscalls/syscall_64.tbl > @@ -327,6 +327,7 @@ > 318 common getrandom sys_getrandom > 319 common memfd_create sys_memfd_create > 320 common kexec_file_load sys_kexec_file_load > +321 64 execveat stub_execveat > > # > # x32-specific system call numbers start at 512 to avoid cache impact > @@ -365,3 +366,4 @@ > 542 x32 getsockopt compat_sys_getsockopt > 543 x32 io_setup compat_sys_io_setup > 544 x32 io_submit compat_sys_io_submit > +545 x32 execveat stub_x32_execveat > diff --git a/arch/x86/um/sys_call_table_64.c b/arch/x86/um/sys_call_table_64.c > index f2f0723070ca..20c3649d0691 100644 > --- a/arch/x86/um/sys_call_table_64.c > +++ b/arch/x86/um/sys_call_table_64.c > @@ -31,6 +31,7 @@ > #define stub_fork sys_fork > #define stub_vfork sys_vfork > #define stub_execve sys_execve > +#define stub_execveat sys_execveat > #define stub_rt_sigreturn sys_rt_sigreturn > > #define __SYSCALL_COMMON(nr, sym, compat) __SYSCALL_64(nr, sym, compat) > diff --git a/fs/exec.c b/fs/exec.c > index a2b42a98c743..92a6e14f096a 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -747,7 +747,7 @@ 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; > @@ -757,10 +757,34 @@ static struct file *do_open_exec(struct filename *name) > .intent = LOOKUP_OPEN, > .lookup_flags = LOOKUP_FOLLOW, > }; > + static const struct open_flags open_exec_nofollow_flags = { > + .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, > + .acc_mode = MAY_EXEC | MAY_OPEN, > + .intent = LOOKUP_OPEN, > + .lookup_flags = 0, > + }; > > - file = do_filp_open(AT_FDCWD, name, &open_exec_flags); > - if (IS_ERR(file)) > - goto out; > + if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0) > + return ERR_PTR(-EINVAL); > + > + if (name->name[0] != '\0') { Is it really necessary to special case AT_EMPTY_PATH here. I would have thought the existing logic in namei.c would have been fine assuning we passed LOOKUP_EMPTY. > + const struct open_flags *oflags = ((flags & AT_SYMLINK_NOFOLLOW) > + ? &open_exec_nofollow_flags > + : &open_exec_flags); > + > + file = do_filp_open(fd, name, oflags); > + if (IS_ERR(file)) > + goto out; > + } else { > + file = fget(fd); > + if (!file) > + return ERR_PTR(-EBADF); > + > + err = inode_permission(file->f_path.dentry->d_inode, > + open_exec_flags.acc_mode); > + if (err) > + goto exit; > + } > > err = -EACCES; > if (!S_ISREG(file_inode(file)->i_mode)) > @@ -769,12 +793,13 @@ static struct file *do_open_exec(struct filename *name) > 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; > > @@ -786,7 +811,7 @@ 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); > > @@ -1422,10 +1447,12 @@ static int exec_binprm(struct linux_binprm *bprm) > /* > * 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; > @@ -1466,7 +1493,7 @@ static int do_execve_common(struct filename *filename, > 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; > @@ -1474,7 +1501,27 @@ static int do_execve_common(struct filename *filename, > sched_exec(); > > bprm->file = file; > - bprm->filename = bprm->interp = filename->name; > + if (fd == AT_FDCWD || filename->name[0] == '/') { > + bprm->filename = filename->name; > + } else { > + /* > + * Build a pathname that reflects how we got to the file, > + * either "/dev/fd/<fd>" (for an empty filename) or > + * "/dev/fd/<fd>/<filename>". > + */ > + pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY); > + if (!pathbuf) { > + retval = -ENOMEM; > + goto out_unmark; > + } > + bprm->filename = pathbuf; > + if (filename->name[0] == '\0') > + sprintf(pathbuf, "/dev/fd/%d", fd); > + else > + snprintf(pathbuf, PATH_MAX, > + "/dev/fd/%d/%s", fd, filename->name); > + } > + bprm->interp = bprm->filename; > > retval = bprm_mm_init(bprm); > if (retval) > @@ -1532,6 +1579,7 @@ out_unmark: > > out_free: > free_bprm(bprm); > + kfree(pathbuf); > > out_files: > if (displaced) > @@ -1547,7 +1595,18 @@ 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 > @@ -1563,7 +1622,23 @@ static int compat_do_execve(struct filename *filename, > .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 > > @@ -1603,6 +1678,20 @@ 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, > @@ -1610,4 +1699,17 @@ COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename, > { > 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 --git a/fs/namei.c b/fs/namei.c > index a7b05bf82d31..553c84d3e0cc 100644 > --- a/fs/namei.c > +++ b/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 --git a/include/linux/compat.h b/include/linux/compat.h > index e6494261eaff..7450ca2ac1fc 100644 > --- a/include/linux/compat.h > +++ b/include/linux/compat.h > @@ -357,6 +357,9 @@ asmlinkage long compat_sys_lseek(unsigned int, compat_off_t, unsigned int); > > 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 --git a/include/linux/fs.h b/include/linux/fs.h > index 94187721ad41..e9818574d738 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -2060,6 +2060,7 @@ extern struct file *file_open_root(struct dentry *, struct vfsmount *, > 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 --git a/include/linux/sched.h b/include/linux/sched.h > index b867a4dab38a..33e056da7d33 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -2430,6 +2430,10 @@ 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 --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index 0f86d85a9ce4..df5422294deb 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -876,4 +876,8 @@ asmlinkage long sys_seccomp(unsigned int op, unsigned int flags, > asmlinkage long sys_getrandom(char __user *buf, size_t count, > unsigned int flags); > > +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 --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h > index 11d11bc5c78f..feef07d29663 100644 > --- a/include/uapi/asm-generic/unistd.h > +++ b/include/uapi/asm-generic/unistd.h > @@ -705,9 +705,11 @@ __SYSCALL(__NR_seccomp, sys_seccomp) > __SYSCALL(__NR_getrandom, sys_getrandom) > #define __NR_memfd_create 279 > __SYSCALL(__NR_memfd_create, sys_memfd_create) > +#define __NR_execveat 280 > +__SC_COMP(__NR_execveat, sys_execveat, compat_sys_execveat) > > #undef __NR_syscalls > -#define __NR_syscalls 280 > +#define __NR_syscalls 281 > > /* > * All syscalls below here should go away really, > diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c > index 391d4ddb6f4b..efb06058ad3e 100644 > --- a/kernel/sys_ni.c > +++ b/kernel/sys_ni.c > @@ -218,3 +218,6 @@ cond_syscall(sys_kcmp); > > /* operate on Secure Computing state */ > cond_syscall(sys_seccomp); > + > +/* execveat */ > +cond_syscall(sys_execveat); > diff --git a/lib/audit.c b/lib/audit.c > index 1d726a22565b..b8fb5ee81e26 100644 > --- a/lib/audit.c > +++ b/lib/audit.c > @@ -54,6 +54,9 @@ int audit_classify_syscall(int abi, unsigned syscall) > case __NR_socketcall: > return 4; > #endif > +#ifdef __NR_execveat > + case __NR_execveat: > +#endif > case __NR_execve: > return 5; > default: -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html