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). Only x86-64, i386 and x32 ABIs are supported in this patch. Based on patches by Meredydd Luff <[email protected]> Signed-off-by: David Drysdale <[email protected]> --- 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/binfmt_em86.c | 4 ++ fs/binfmt_misc.c | 4 ++ fs/binfmt_script.c | 10 ++++ fs/exec.c | 110 +++++++++++++++++++++++++++++++++----- 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 | 4 ++ include/uapi/asm-generic/unistd.h | 4 +- kernel/sys_ni.c | 3 ++ lib/audit.c | 3 ++ 20 files changed, 176 insertions(+), 15 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/binfmt_em86.c b/fs/binfmt_em86.c index f37b08cea1f7..490538536cb4 100644 --- a/fs/binfmt_em86.c +++ b/fs/binfmt_em86.c @@ -42,6 +42,10 @@ static int load_em86(struct linux_binprm *bprm) 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 --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c index b60500300dd7..e659f5562356 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -127,6 +127,10 @@ static int load_misc_binary(struct linux_binprm *bprm) 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 --git a/fs/binfmt_script.c b/fs/binfmt_script.c index 5027a3e14922..afdf4e3cafc2 100644 --- a/fs/binfmt_script.c +++ b/fs/binfmt_script.c @@ -24,6 +24,16 @@ static int load_script(struct linux_binprm *bprm) 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 --git a/fs/exec.c b/fs/exec.c index a2b42a98c743..500363723b57 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -747,18 +747,25 @@ 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; @@ -769,12 +776,13 @@ 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 +794,7 @@ 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 +1430,12 @@ 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 +1476,7 @@ 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 +1484,26 @@ 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 { + 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, current->files->fdt)) + bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE; + bprm->filename = pathbuf; + } + bprm->interp = bprm->filename; retval = bprm_mm_init(bprm); if (retval) @@ -1532,6 +1561,7 @@ out_unmark: out_free: free_bprm(bprm); + kfree(pathbuf); out_files: if (displaced) @@ -1547,7 +1577,18 @@ 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 +1604,23 @@ 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 +1660,20 @@ 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 +1681,17 @@ 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/binfmts.h b/include/linux/binfmts.h index 61f29e5ea840..576e4639ca60 100644 --- a/include/linux/binfmts.h +++ b/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 --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: -- 2.1.0.rc2.206.gedb03e5 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
