fs: remove uselib() system call

This system call has been deprecated for quite a while now.
Let's try and remove it from the kernel completely.

Link: https://lore.kernel.org/20250415-kanufahren-besten-02ac00e6becd@brauner
Acked-by: Kees Cook <kees@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

arch/m68k/configs/amcore_defconfig

@@ -2,7 +2,6 @@ CONFIG_LOCALVERSION="amcore-002"
 CONFIG_DEFAULT_HOSTNAME="amcore"
 CONFIG_SYSVIPC=y
 # CONFIG_FHANDLE is not set
-# CONFIG_USELIB is not set
 CONFIG_LOG_BUF_SHIFT=14
 CONFIG_CC_OPTIMIZE_FOR_SIZE=y
 # CONFIG_AIO is not set

arch/x86/configs/i386_defconfig

@@ -1,7 +1,6 @@
 CONFIG_WERROR=y
 CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
-CONFIG_USELIB=y
 CONFIG_AUDIT=y
 CONFIG_NO_HZ=y
 CONFIG_HIGH_RES_TIMERS=y

arch/xtensa/configs/cadence_csp_defconfig

@@ -1,6 +1,5 @@
 CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
-CONFIG_USELIB=y
 CONFIG_NO_HZ_IDLE=y
 CONFIG_HIGH_RES_TIMERS=y
 CONFIG_IRQ_TIME_ACCOUNTING=y

fs/binfmt_elf.c

@@ -68,12 +68,6 @@
 
 static int load_elf_binary(struct linux_binprm *bprm);
 
-#ifdef CONFIG_USELIB
-static int load_elf_library(struct file *);
-#else
-#define load_elf_library NULL
-#endif
-
 /*
  * If we don't support core dumping, then supply a NULL so we
  * don't even try.
@@ -101,7 +95,6 @@ static int elf_core_dump(struct coredump_params *cprm);
 static struct linux_binfmt elf_format = {
 	.module		= THIS_MODULE,
 	.load_binary	= load_elf_binary,
-	.load_shlib	= load_elf_library,
 #ifdef CONFIG_COREDUMP
 	.core_dump	= elf_core_dump,
 	.min_coredump	= ELF_EXEC_PAGESIZE,
@@ -1361,75 +1354,6 @@ out_free_ph:
 	goto out;
 }
 
-#ifdef CONFIG_USELIB
-/* This is really simpleminded and specialized - we are loading an
-   a.out library that is given an ELF header. */
-static int load_elf_library(struct file *file)
-{
-	struct elf_phdr *elf_phdata;
-	struct elf_phdr *eppnt;
-	int retval, error, i, j;
-	struct elfhdr elf_ex;
-
-	error = -ENOEXEC;
-	retval = elf_read(file, &elf_ex, sizeof(elf_ex), 0);
-	if (retval < 0)
-		goto out;
-
-	if (memcmp(elf_ex.e_ident, ELFMAG, SELFMAG) != 0)
-		goto out;
-
-	/* First of all, some simple consistency checks */
-	if (elf_ex.e_type != ET_EXEC || elf_ex.e_phnum > 2 ||
-	    !elf_check_arch(&elf_ex) || !file->f_op->mmap)
-		goto out;
-	if (elf_check_fdpic(&elf_ex))
-		goto out;
-
-	/* Now read in all of the header information */
-
-	j = sizeof(struct elf_phdr) * elf_ex.e_phnum;
-	/* j < ELF_MIN_ALIGN because elf_ex.e_phnum <= 2 */
-
-	error = -ENOMEM;
-	elf_phdata = kmalloc(j, GFP_KERNEL);
-	if (!elf_phdata)
-		goto out;
-
-	eppnt = elf_phdata;
-	error = -ENOEXEC;
-	retval = elf_read(file, eppnt, j, elf_ex.e_phoff);
-	if (retval < 0)
-		goto out_free_ph;
-
-	for (j = 0, i = 0; i<elf_ex.e_phnum; i++)
-		if ((eppnt + i)->p_type == PT_LOAD)
-			j++;
-	if (j != 1)
-		goto out_free_ph;
-
-	while (eppnt->p_type != PT_LOAD)
-		eppnt++;
-
-	/* Now use mmap to map the library into memory. */
-	error = elf_load(file, ELF_PAGESTART(eppnt->p_vaddr),
-			eppnt,
-			PROT_READ | PROT_WRITE | PROT_EXEC,
-			MAP_FIXED_NOREPLACE | MAP_PRIVATE,
-			0);
-
-	if (error != ELF_PAGESTART(eppnt->p_vaddr))
-		goto out_free_ph;
-
-	error = 0;
-
-out_free_ph:
-	kfree(elf_phdata);
-out:
-	return error;
-}
-#endif /* #ifdef CONFIG_USELIB */
-
 #ifdef CONFIG_ELF_CORE
 /*
  * ELF core dumper

fs/exec.c

@@ -115,66 +115,6 @@ bool path_noexec(const struct path *path)
 	       (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
 }
 
-#ifdef CONFIG_USELIB
-/*
- * Note that a shared library must be both readable and executable due to
- * security reasons.
- *
- * Also note that we take the address to load from the file itself.
- */
-SYSCALL_DEFINE1(uselib, const char __user *, library)
-{
-	struct linux_binfmt *fmt;
-	struct file *file;
-	struct filename *tmp = getname(library);
-	int error = PTR_ERR(tmp);
-	static const struct open_flags uselib_flags = {
-		.open_flag = O_LARGEFILE | O_RDONLY,
-		.acc_mode = MAY_READ | MAY_EXEC,
-		.intent = LOOKUP_OPEN,
-		.lookup_flags = LOOKUP_FOLLOW,
-	};
-
-	if (IS_ERR(tmp))
-		goto out;
-
-	file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
-	putname(tmp);
-	error = PTR_ERR(file);
-	if (IS_ERR(file))
-		goto out;
-
-	/*
-	 * Check do_open_execat() for an explanation.
-	 */
-	error = -EACCES;
-	if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)) ||
-	    path_noexec(&file->f_path))
-		goto exit;
-
-	error = -ENOEXEC;
-
-	read_lock(&binfmt_lock);
-	list_for_each_entry(fmt, &formats, lh) {
-		if (!fmt->load_shlib)
-			continue;
-		if (!try_module_get(fmt->module))
-			continue;
-		read_unlock(&binfmt_lock);
-		error = fmt->load_shlib(file);
-		read_lock(&binfmt_lock);
-		put_binfmt(fmt);
-		if (error != -ENOEXEC)
-			break;
-	}
-	read_unlock(&binfmt_lock);
-exit:
-	fput(file);
-out:
-	return error;
-}
-#endif /* #ifdef CONFIG_USELIB */
-
 #ifdef CONFIG_MMU
 /*
  * The nascent bprm->mm is not visible until exec_mmap() but it can

include/linux/binfmts.h

@@ -90,7 +90,6 @@ struct linux_binfmt {
 	struct list_head lh;
 	struct module *module;
 	int (*load_binary)(struct linux_binprm *);
-	int (*load_shlib)(struct file *);
 #ifdef CONFIG_COREDUMP
 	int (*core_dump)(struct coredump_params *cprm);
 	unsigned long min_coredump;	/* minimal dump size */

init/Kconfig

@@ -479,16 +479,6 @@ config CROSS_MEMORY_ATTACH
 	  to directly read from or write to another process' address space.
 	  See the man page for more details.
 
-config USELIB
-	bool "uselib syscall (for libc5 and earlier)"
-	default ALPHA || M68K || SPARC
-	help
-	  This option enables the uselib syscall, a system call used in the
-	  dynamic linker from libc5 and earlier.  glibc does not use this
-	  system call.  If you intend to run programs built on libc5 or
-	  earlier, you may need to enable this syscall.  Current systems
-	  running glibc can safely disable this.
-
 config AUDIT
 	bool "Auditing support"
 	depends on NET

tools/testing/selftests/bpf/config.aarch64

@@ -158,7 +158,6 @@ CONFIG_TRANSPARENT_HUGEPAGE=y
 CONFIG_TUN=y
 CONFIG_UNIX=y
 CONFIG_UPROBES=y
-CONFIG_USELIB=y
 CONFIG_USER_NS=y
 CONFIG_VETH=y
 CONFIG_VLAN_8021Q=y

tools/testing/selftests/bpf/config.s390x

@@ -128,7 +128,6 @@ CONFIG_TRANSPARENT_HUGEPAGE=y
 CONFIG_TUN=y
 CONFIG_UNIX=y
 CONFIG_UPROBES=y
-CONFIG_USELIB=y
 CONFIG_USER_NS=y
 CONFIG_VETH=y
 CONFIG_VLAN_8021Q=y