exec: unify do_execve/compat_do_execve code
Add the appropriate members into struct user_arg_ptr and teach get_user_arg_ptr() to handle is_compat = T case correctly. This allows us to remove the compat_do_execve() code from fs/compat.c and reimplement compat_do_execve() as the trivial wrapper on top of do_execve_common(is_compat => true). In fact, this fixes another (minor) bug. "compat_uptr_t str" can overflow after "str += len" in compat_copy_strings() if a 64bit application execs via sys32_execve(). Unexport acct_arg_size() and get_arg_page(), fs/compat.c doesn't need them any longer. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Tested-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
This commit is contained in:
Oleg Nesterov
parent
ba2d01629d
commit
0e028465d1
3 changed files with 50 additions and 251 deletions
235
fs/compat.c
235
fs/compat.c
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@ -1306,241 +1306,6 @@ compat_sys_openat(unsigned int dfd, const char __user *filename, int flags, int
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return do_sys_open(dfd, filename, flags, mode);
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}
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/*
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* compat_count() counts the number of arguments/envelopes. It is basically
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* a copy of count() from fs/exec.c, except that it works with 32 bit argv
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* and envp pointers.
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*/
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static int compat_count(compat_uptr_t __user *argv, int max)
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{
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int i = 0;
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if (argv != NULL) {
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for (;;) {
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compat_uptr_t p;
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if (get_user(p, argv))
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return -EFAULT;
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if (!p)
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break;
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argv++;
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if (i++ >= max)
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return -E2BIG;
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if (fatal_signal_pending(current))
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return -ERESTARTNOHAND;
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cond_resched();
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}
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}
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return i;
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}
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/*
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* compat_copy_strings() is basically a copy of copy_strings() from fs/exec.c
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* except that it works with 32 bit argv and envp pointers.
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*/
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static int compat_copy_strings(int argc, compat_uptr_t __user *argv,
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struct linux_binprm *bprm)
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{
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struct page *kmapped_page = NULL;
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char *kaddr = NULL;
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unsigned long kpos = 0;
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int ret;
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while (argc-- > 0) {
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compat_uptr_t str;
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int len;
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unsigned long pos;
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if (get_user(str, argv+argc) ||
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!(len = strnlen_user(compat_ptr(str), MAX_ARG_STRLEN))) {
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ret = -EFAULT;
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goto out;
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}
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if (len > MAX_ARG_STRLEN) {
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ret = -E2BIG;
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goto out;
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}
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/* We're going to work our way backwords. */
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pos = bprm->p;
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str += len;
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bprm->p -= len;
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while (len > 0) {
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int offset, bytes_to_copy;
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if (fatal_signal_pending(current)) {
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ret = -ERESTARTNOHAND;
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goto out;
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}
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cond_resched();
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offset = pos % PAGE_SIZE;
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if (offset == 0)
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offset = PAGE_SIZE;
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bytes_to_copy = offset;
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if (bytes_to_copy > len)
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bytes_to_copy = len;
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offset -= bytes_to_copy;
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pos -= bytes_to_copy;
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str -= bytes_to_copy;
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len -= bytes_to_copy;
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if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
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struct page *page;
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page = get_arg_page(bprm, pos, 1);
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if (!page) {
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ret = -E2BIG;
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goto out;
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}
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if (kmapped_page) {
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flush_kernel_dcache_page(kmapped_page);
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kunmap(kmapped_page);
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put_page(kmapped_page);
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}
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kmapped_page = page;
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kaddr = kmap(kmapped_page);
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kpos = pos & PAGE_MASK;
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flush_cache_page(bprm->vma, kpos,
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page_to_pfn(kmapped_page));
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}
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if (copy_from_user(kaddr+offset, compat_ptr(str),
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bytes_to_copy)) {
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ret = -EFAULT;
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goto out;
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}
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}
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}
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ret = 0;
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out:
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if (kmapped_page) {
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flush_kernel_dcache_page(kmapped_page);
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kunmap(kmapped_page);
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put_page(kmapped_page);
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}
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return ret;
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}
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/*
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* compat_do_execve() is mostly a copy of do_execve(), with the exception
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* that it processes 32 bit argv and envp pointers.
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*/
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int compat_do_execve(char * filename,
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compat_uptr_t __user *argv,
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compat_uptr_t __user *envp,
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struct pt_regs * regs)
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{
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struct linux_binprm *bprm;
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struct file *file;
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struct files_struct *displaced;
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bool clear_in_exec;
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int retval;
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retval = unshare_files(&displaced);
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if (retval)
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goto out_ret;
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retval = -ENOMEM;
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bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
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if (!bprm)
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goto out_files;
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retval = prepare_bprm_creds(bprm);
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if (retval)
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goto out_free;
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retval = check_unsafe_exec(bprm);
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if (retval < 0)
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goto out_free;
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clear_in_exec = retval;
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current->in_execve = 1;
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file = open_exec(filename);
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retval = PTR_ERR(file);
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if (IS_ERR(file))
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goto out_unmark;
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sched_exec();
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bprm->file = file;
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bprm->filename = filename;
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bprm->interp = filename;
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retval = bprm_mm_init(bprm);
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if (retval)
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goto out_file;
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bprm->argc = compat_count(argv, MAX_ARG_STRINGS);
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if ((retval = bprm->argc) < 0)
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goto out;
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bprm->envc = compat_count(envp, MAX_ARG_STRINGS);
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if ((retval = bprm->envc) < 0)
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goto out;
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retval = prepare_binprm(bprm);
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if (retval < 0)
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goto out;
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retval = copy_strings_kernel(1, &bprm->filename, bprm);
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if (retval < 0)
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goto out;
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bprm->exec = bprm->p;
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retval = compat_copy_strings(bprm->envc, envp, bprm);
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if (retval < 0)
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goto out;
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retval = compat_copy_strings(bprm->argc, argv, bprm);
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if (retval < 0)
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goto out;
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retval = search_binary_handler(bprm, regs);
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if (retval < 0)
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goto out;
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/* execve succeeded */
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current->fs->in_exec = 0;
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current->in_execve = 0;
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acct_update_integrals(current);
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free_bprm(bprm);
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if (displaced)
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put_files_struct(displaced);
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return retval;
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out:
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if (bprm->mm) {
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acct_arg_size(bprm, 0);
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mmput(bprm->mm);
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}
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out_file:
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if (bprm->file) {
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allow_write_access(bprm->file);
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fput(bprm->file);
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}
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out_unmark:
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if (clear_in_exec)
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current->fs->in_exec = 0;
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current->in_execve = 0;
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out_free:
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free_bprm(bprm);
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out_files:
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if (displaced)
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reset_files_struct(displaced);
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out_ret:
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return retval;
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}
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#define __COMPAT_NFDBITS (8 * sizeof(compat_ulong_t))
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static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
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62
fs/exec.c
62
fs/exec.c
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@ -55,6 +55,7 @@
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#include <linux/fs_struct.h>
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#include <linux/pipe_fs_i.h>
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#include <linux/oom.h>
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#include <linux/compat.h>
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#include <asm/uaccess.h>
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#include <asm/mmu_context.h>
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@ -167,7 +168,7 @@ SYSCALL_DEFINE1(uselib, const char __user *, library)
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#ifdef CONFIG_MMU
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void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
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static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
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{
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struct mm_struct *mm = current->mm;
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long diff = (long)(pages - bprm->vma_pages);
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@ -186,7 +187,7 @@ void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
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#endif
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}
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struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
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static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
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int write)
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{
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struct page *page;
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@ -305,11 +306,11 @@ static bool valid_arg_len(struct linux_binprm *bprm, long len)
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#else
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void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
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static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
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{
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}
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struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
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static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
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int write)
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{
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struct page *page;
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@ -399,17 +400,36 @@ int bprm_mm_init(struct linux_binprm *bprm)
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}
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struct user_arg_ptr {
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const char __user *const __user *native;
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#ifdef CONFIG_COMPAT
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bool is_compat;
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#endif
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union {
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const char __user *const __user *native;
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#ifdef CONFIG_COMPAT
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compat_uptr_t __user *compat;
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#endif
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} ptr;
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};
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static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
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{
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const char __user *ptr;
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const char __user *native;
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if (get_user(ptr, argv.native + nr))
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#ifdef CONFIG_COMPAT
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if (unlikely(argv.is_compat)) {
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compat_uptr_t compat;
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if (get_user(compat, argv.ptr.compat + nr))
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return ERR_PTR(-EFAULT);
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return compat_ptr(compat);
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}
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#endif
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if (get_user(native, argv.ptr.native + nr))
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return ERR_PTR(-EFAULT);
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return ptr;
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return native;
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}
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/*
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@ -419,7 +439,7 @@ static int count(struct user_arg_ptr argv, int max)
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{
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int i = 0;
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if (argv.native != NULL) {
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if (argv.ptr.native != NULL) {
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for (;;) {
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const char __user *p = get_user_arg_ptr(argv, i);
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@ -542,7 +562,7 @@ int copy_strings_kernel(int argc, const char *const *__argv,
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int r;
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mm_segment_t oldfs = get_fs();
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struct user_arg_ptr argv = {
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.native = (const char __user *const __user *)__argv,
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.ptr.native = (const char __user *const __user *)__argv,
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};
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set_fs(KERNEL_DS);
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@ -1516,11 +1536,29 @@ int do_execve(const char *filename,
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const char __user *const __user *__envp,
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struct pt_regs *regs)
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{
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struct user_arg_ptr argv = { .native = __argv };
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struct user_arg_ptr envp = { .native = __envp };
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struct user_arg_ptr argv = { .ptr.native = __argv };
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struct user_arg_ptr envp = { .ptr.native = __envp };
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return do_execve_common(filename, argv, envp, regs);
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}
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#ifdef CONFIG_COMPAT
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int compat_do_execve(char *filename,
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compat_uptr_t __user *__argv,
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compat_uptr_t __user *__envp,
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struct pt_regs *regs)
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{
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struct user_arg_ptr argv = {
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.is_compat = true,
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.ptr.compat = __argv,
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};
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struct user_arg_ptr envp = {
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.is_compat = true,
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.ptr.compat = __envp,
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};
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return do_execve_common(filename, argv, envp, regs);
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}
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#endif
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void set_binfmt(struct linux_binfmt *new)
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{
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struct mm_struct *mm = current->mm;
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@ -60,10 +60,6 @@ struct linux_binprm {
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unsigned long loader, exec;
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};
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extern void acct_arg_size(struct linux_binprm *bprm, unsigned long pages);
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extern struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
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int write);
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#define BINPRM_FLAGS_ENFORCE_NONDUMP_BIT 0
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#define BINPRM_FLAGS_ENFORCE_NONDUMP (1 << BINPRM_FLAGS_ENFORCE_NONDUMP_BIT)
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