1 files changed, 109 insertions, 74 deletions

diff --git a/fs/exec.c b/fs/exec.c
index ec5df9a38313..1f59ea079cbb 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -55,6 +55,7 @@
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
 #include <asm/tlb.h>
+#include "internal.h"
 
 #ifdef __alpha__
 /* for /sbin/loader handling in search_binary_handler() */
@@ -980,7 +981,7 @@ int flush_old_exec(struct linux_binprm * bprm)
 	/* This is the point of no return */
 	current->sas_ss_sp = current->sas_ss_size = 0;
 
-	if (current->euid == current->uid && current->egid == current->gid)
+	if (current_euid() == current_uid() && current_egid() == current_gid())
 		set_dumpable(current->mm, 1);
 	else
 		set_dumpable(current->mm, suid_dumpable);
@@ -1007,16 +1008,17 @@ int flush_old_exec(struct linux_binprm * bprm)
 	 */
 	current->mm->task_size = TASK_SIZE;
 
-	if (bprm->e_uid != current->euid || bprm->e_gid != current->egid) {
-		suid_keys(current);
-		set_dumpable(current->mm, suid_dumpable);
+	/* install the new credentials */
+	if (bprm->cred->uid != current_euid() ||
+	    bprm->cred->gid != current_egid()) {
 		current->pdeath_signal = 0;
 	} else if (file_permission(bprm->file, MAY_READ) ||
-			(bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
-		suid_keys(current);
+		   bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
 		set_dumpable(current->mm, suid_dumpable);
 	}
 
+	current->personality &= ~bprm->per_clear;
+
 	/* An exec changes our domain. We are no longer part of the thread
 	   group */
 
@@ -1033,13 +1035,50 @@ out:
 
 EXPORT_SYMBOL(flush_old_exec);
 
+/*
+ * install the new credentials for this executable
+ */
+void install_exec_creds(struct linux_binprm *bprm)
+{
+	security_bprm_committing_creds(bprm);
+
+	commit_creds(bprm->cred);
+	bprm->cred = NULL;
+
+	/* cred_exec_mutex must be held at least to this point to prevent
+	 * ptrace_attach() from altering our determination of the task's
+	 * credentials; any time after this it may be unlocked */
+
+	security_bprm_committed_creds(bprm);
+}
+EXPORT_SYMBOL(install_exec_creds);
+
+/*
+ * determine how safe it is to execute the proposed program
+ * - the caller must hold current->cred_exec_mutex to protect against
+ *   PTRACE_ATTACH
+ */
+void check_unsafe_exec(struct linux_binprm *bprm)
+{
+	struct task_struct *p = current;
+
+	bprm->unsafe = tracehook_unsafe_exec(p);
+
+	if (atomic_read(&p->fs->count) > 1 ||
+	    atomic_read(&p->files->count) > 1 ||
+	    atomic_read(&p->sighand->count) > 1)
+		bprm->unsafe |= LSM_UNSAFE_SHARE;
+}
+
 /* 
  * Fill the binprm structure from the inode. 
  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
+ *
+ * This may be called multiple times for binary chains (scripts for example).
  */
 int prepare_binprm(struct linux_binprm *bprm)
 {
-	int mode;
+	umode_t mode;
 	struct inode * inode = bprm->file->f_path.dentry->d_inode;
 	int retval;
 
@@ -1047,14 +1086,15 @@ int prepare_binprm(struct linux_binprm *bprm)
 	if (bprm->file->f_op == NULL)
 		return -EACCES;
 
-	bprm->e_uid = current->euid;
-	bprm->e_gid = current->egid;
+	/* clear any previous set[ug]id data from a previous binary */
+	bprm->cred->euid = current_euid();
+	bprm->cred->egid = current_egid();
 
-	if(!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
+	if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
 		/* Set-uid? */
 		if (mode & S_ISUID) {
-			current->personality &= ~PER_CLEAR_ON_SETID;
-			bprm->e_uid = inode->i_uid;
+			bprm->per_clear |= PER_CLEAR_ON_SETID;
+			bprm->cred->euid = inode->i_uid;
 		}
 
 		/* Set-gid? */
@@ -1064,52 +1104,23 @@ int prepare_binprm(struct linux_binprm *bprm)
 		 * executable.
 		 */
 		if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
-			current->personality &= ~PER_CLEAR_ON_SETID;
-			bprm->e_gid = inode->i_gid;
+			bprm->per_clear |= PER_CLEAR_ON_SETID;
+			bprm->cred->egid = inode->i_gid;
 		}
 	}
 
 	/* fill in binprm security blob */
-	retval = security_bprm_set(bprm);
+	retval = security_bprm_set_creds(bprm);
 	if (retval)
 		return retval;
+	bprm->cred_prepared = 1;
 
-	memset(bprm->buf,0,BINPRM_BUF_SIZE);
-	return kernel_read(bprm->file,0,bprm->buf,BINPRM_BUF_SIZE);
+	memset(bprm->buf, 0, BINPRM_BUF_SIZE);
+	return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
 }
 
 EXPORT_SYMBOL(prepare_binprm);
 
-static int unsafe_exec(struct task_struct *p)
-{
-	int unsafe = tracehook_unsafe_exec(p);
-
-	if (atomic_read(&p->fs->count) > 1 ||
-	    atomic_read(&p->files->count) > 1 ||
-	    atomic_read(&p->sighand->count) > 1)
-		unsafe |= LSM_UNSAFE_SHARE;
-
-	return unsafe;
-}
-
-void compute_creds(struct linux_binprm *bprm)
-{
-	int unsafe;
-
-	if (bprm->e_uid != current->uid) {
-		suid_keys(current);
-		current->pdeath_signal = 0;
-	}
-	exec_keys(current);
-
-	task_lock(current);
-	unsafe = unsafe_exec(current);
-	security_bprm_apply_creds(bprm, unsafe);
-	task_unlock(current);
-	security_bprm_post_apply_creds(bprm);
-}
-EXPORT_SYMBOL(compute_creds);
-
 /*
  * Arguments are '\0' separated strings found at the location bprm->p
  * points to; chop off the first by relocating brpm->p to right after
@@ -1270,6 +1281,8 @@ EXPORT_SYMBOL(search_binary_handler);
 void free_bprm(struct linux_binprm *bprm)
 {
 	free_arg_pages(bprm);
+	if (bprm->cred)
+		abort_creds(bprm->cred);
 	kfree(bprm);
 }
 
@@ -1295,10 +1308,20 @@ int do_execve(char * filename,
 	if (!bprm)
 		goto out_files;
 
+	retval = mutex_lock_interruptible(&current->cred_exec_mutex);
+	if (retval < 0)
+		goto out_free;
+
+	retval = -ENOMEM;
+	bprm->cred = prepare_exec_creds();
+	if (!bprm->cred)
+		goto out_unlock;
+	check_unsafe_exec(bprm);
+
 	file = open_exec(filename);
 	retval = PTR_ERR(file);
 	if (IS_ERR(file))
-		goto out_kfree;
+		goto out_unlock;
 
 	sched_exec();
 
@@ -1312,14 +1335,10 @@ int do_execve(char * filename,
 
 	bprm->argc = count(argv, MAX_ARG_STRINGS);
 	if ((retval = bprm->argc) < 0)
-		goto out_mm;
+		goto out;
 
 	bprm->envc = count(envp, MAX_ARG_STRINGS);
 	if ((retval = bprm->envc) < 0)
-		goto out_mm;
-
-	retval = security_bprm_alloc(bprm);
-	if (retval)
 		goto out;
 
 	retval = prepare_binprm(bprm);
@@ -1341,21 +1360,18 @@ int do_execve(char * filename,
 
 	current->flags &= ~PF_KTHREAD;
 	retval = search_binary_handler(bprm,regs);
-	if (retval >= 0) {
-		/* execve success */
-		security_bprm_free(bprm);
-		acct_update_integrals(current);
-		free_bprm(bprm);
-		if (displaced)
-			put_files_struct(displaced);
-		return retval;
-	}
+	if (retval < 0)
+		goto out;
 
-out:
-	if (bprm->security)
-		security_bprm_free(bprm);
+	/* execve succeeded */
+	mutex_unlock(&current->cred_exec_mutex);
+	acct_update_integrals(current);
+	free_bprm(bprm);
+	if (displaced)
+		put_files_struct(displaced);
+	return retval;
 
-out_mm:
+out:
 	if (bprm->mm)
 		mmput (bprm->mm);
 
@@ -1364,7 +1380,11 @@ out_file:
 		allow_write_access(bprm->file);
 		fput(bprm->file);
 	}
-out_kfree:
+
+out_unlock:
+	mutex_unlock(&current->cred_exec_mutex);
+
+out_free:
 	free_bprm(bprm);
 
 out_files:
@@ -1396,6 +1416,7 @@ EXPORT_SYMBOL(set_binfmt);
  */
 static int format_corename(char *corename, long signr)
 {
+	const struct cred *cred = current_cred();
 	const char *pat_ptr = core_pattern;
 	int ispipe = (*pat_ptr == '|');
 	char *out_ptr = corename;
@@ -1432,7 +1453,7 @@ static int format_corename(char *corename, long signr)
 			/* uid */
 			case 'u':
 				rc = snprintf(out_ptr, out_end - out_ptr,
-					      "%d", current->uid);
+					      "%d", cred->uid);
 				if (rc > out_end - out_ptr)
 					goto out;
 				out_ptr += rc;
@@ -1440,7 +1461,7 @@ static int format_corename(char *corename, long signr)
 			/* gid */
 			case 'g':
 				rc = snprintf(out_ptr, out_end - out_ptr,
-					      "%d", current->gid);
+					      "%d", cred->gid);
 				if (rc > out_end - out_ptr)
 					goto out;
 				out_ptr += rc;
@@ -1716,8 +1737,9 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
 	struct linux_binfmt * binfmt;
 	struct inode * inode;
 	struct file * file;
+	const struct cred *old_cred;
+	struct cred *cred;
 	int retval = 0;
-	int fsuid = current->fsuid;
 	int flag = 0;
 	int ispipe = 0;
 	unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
@@ -1730,12 +1752,20 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
 	binfmt = current->binfmt;
 	if (!binfmt || !binfmt->core_dump)
 		goto fail;
+
+	cred = prepare_creds();
+	if (!cred) {
+		retval = -ENOMEM;
+		goto fail;
+	}
+
 	down_write(&mm->mmap_sem);
 	/*
 	 * If another thread got here first, or we are not dumpable, bail out.
 	 */
 	if (mm->core_state || !get_dumpable(mm)) {
 		up_write(&mm->mmap_sem);
+		put_cred(cred);
 		goto fail;
 	}
 
@@ -1746,12 +1776,16 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
 	 */
 	if (get_dumpable(mm) == 2) {	/* Setuid core dump mode */
 		flag = O_EXCL;		/* Stop rewrite attacks */
-		current->fsuid = 0;	/* Dump root private */
+		cred->fsuid = 0;	/* Dump root private */
 	}
 
 	retval = coredump_wait(exit_code, &core_state);
-	if (retval < 0)
+	if (retval < 0) {
+		put_cred(cred);
 		goto fail;
+	}
+
+	old_cred = override_creds(cred);
 
 	/*
 	 * Clear any false indication of pending signals that might
@@ -1823,7 +1857,7 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
 	 * Dont allow local users get cute and trick others to coredump
 	 * into their pre-created files:
 	 */
-	if (inode->i_uid != current->fsuid)
+	if (inode->i_uid != current_fsuid())
 		goto close_fail;
 	if (!file->f_op)
 		goto close_fail;
@@ -1842,7 +1876,8 @@ fail_unlock:
 	if (helper_argv)
 		argv_free(helper_argv);
 
-	current->fsuid = fsuid;
+	revert_creds(old_cred);
+	put_cred(cred);
 	coredump_finish(mm);
 fail:
 	return retval;