#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fdtable.h>
+#include <linux/freezer.h>
#include <linux/mm.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/pipe_fs_i.h>
#include <linux/oom.h>
#include <linux/compat.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/path.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
return res;
}
+static void bprm_fill_uid(struct linux_binprm *bprm)
+{
+ struct inode *inode;
+ unsigned int mode;
+ uid_t uid;
+ gid_t gid;
+
+ /* 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)
+ return;
+
+ inode = bprm->file->f_path.dentry->d_inode;
+ mode = ACCESS_ONCE(inode->i_mode);
+ if (!(mode & (S_ISUID|S_ISGID)))
+ return;
+
+ /* Be careful if suid/sgid is set */
+ mutex_lock(&inode->i_mutex);
+
+ /* reload atomically mode/uid/gid now that lock held */
+ mode = inode->i_mode;
+ uid = inode->i_uid;
+ gid = inode->i_gid;
+ mutex_unlock(&inode->i_mutex);
+
+ if (mode & S_ISUID) {
+ bprm->per_clear |= PER_CLEAR_ON_SETID;
+ bprm->cred->euid = uid;
+ }
+
+ if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
+ bprm->per_clear |= PER_CLEAR_ON_SETID;
+ bprm->cred->egid = gid;
+ }
+}
+
/*
* Fill the binprm structure from the inode.
* Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
*/
int prepare_binprm(struct linux_binprm *bprm)
{
- umode_t mode;
- struct inode * inode = bprm->file->f_path.dentry->d_inode;
int retval;
- mode = inode->i_mode;
if (bprm->file->f_op == NULL)
return -EACCES;
- /* 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)) {
- /* Set-uid? */
- if (mode & S_ISUID) {
- bprm->per_clear |= PER_CLEAR_ON_SETID;
- bprm->cred->euid = inode->i_uid;
- }
-
- /* Set-gid? */
- /*
- * If setgid is set but no group execute bit then this
- * is a candidate for mandatory locking, not a setgid
- * executable.
- */
- if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
- bprm->per_clear |= PER_CLEAR_ON_SETID;
- bprm->cred->egid = inode->i_gid;
- }
- }
+ bprm_fill_uid(bprm);
/* fill in binprm security blob */
retval = security_bprm_set_creds(bprm);
complete(vfork_done);
}
- if (core_waiters)
+ if (core_waiters > 0) {
+ freezer_do_not_count();
wait_for_completion(&core_state->startup);
+ freezer_count();
+ }
fail:
return core_waiters;
}
return (ret >= 2) ? 2 : ret;
}
+/*
+ * This returns the actual value of the suid_dumpable flag. For things
+ * that are using this for checking for privilege transitions, it must
+ * test against SUID_DUMP_USER rather than treating it as a boolean
+ * value.
+ */
int get_dumpable(struct mm_struct *mm)
{
return __get_dumpable(mm->flags);
const struct cred *old_cred;
struct cred *cred;
int retval = 0;
- int flag = 0;
int ispipe;
+ /* require nonrelative corefile path and be extra careful */
+ bool need_suid_safe = false;
static atomic_t core_dump_count = ATOMIC_INIT(0);
struct coredump_params cprm = {
.signr = signr,
if (!cred)
goto fail;
/*
- * We cannot trust fsuid as being the "true" uid of the
- * process nor do we know its entire history. We only know it
- * was tainted so we dump it as root in mode 2.
+ * We cannot trust fsuid as being the "true" uid of the process
+ * nor do we know its entire history. We only know it was tainted
+ * so we dump it as root in mode 2, and only into a controlled
+ * environment (pipe handler or fully qualified path).
*/
if (__get_dumpable(cprm.mm_flags) == 2) {
/* Setuid core dump mode */
- flag = O_EXCL; /* Stop rewrite attacks */
cred->fsuid = 0; /* Dump root private */
+ need_suid_safe = true;
}
retval = coredump_wait(exit_code, &core_state);
}
} else {
struct inode *inode;
+ int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
+ O_LARGEFILE | O_EXCL;
if (cprm.limit < binfmt->min_coredump)
goto fail_unlock;
- cprm.file = filp_open(cn.corename,
- O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
- 0600);
+ if (need_suid_safe && cn.corename[0] != '/') {
+ printk(KERN_WARNING "Pid %d(%s) can only dump core "\
+ "to fully qualified path!\n",
+ task_tgid_vnr(current), current->comm);
+ printk(KERN_WARNING "Skipping core dump\n");
+ goto fail_unlock;
+ }
+
+ /*
+ * Unlink the file if it exists unless this is a SUID
+ * binary - in that case, we're running around with root
+ * privs and don't want to unlink another user's coredump.
+ */
+ if (!need_suid_safe) {
+ mm_segment_t old_fs;
+
+ old_fs = get_fs();
+ set_fs(KERNEL_DS);
+ /*
+ * If it doesn't exist, that's fine. If there's some
+ * other problem, we'll catch it at the filp_open().
+ */
+ (void) sys_unlink((const char __user *)cn.corename);
+ set_fs(old_fs);
+ }
+
+ /*
+ * There is a race between unlinking and creating the
+ * file, but if that causes an EEXIST here, that's
+ * fine - another process raced with us while creating
+ * the corefile, and the other process won. To userspace,
+ * what matters is that at least one of the two processes
+ * writes its coredump successfully, not which one.
+ */
+ if (need_suid_safe) {
+ /*
+ * Using user namespaces, normal user tasks can change
+ * their current->fs->root to point to arbitrary
+ * directories. Since the intention of the "only dump
+ * with a fully qualified path" rule is to control where
+ * coredumps may be placed using root privileges,
+ * current->fs->root must not be used. Instead, use the
+ * root directory of init_task.
+ */
+ struct path root;
+
+ task_lock(&init_task);
+ get_fs_root(init_task.fs, &root);
+ task_unlock(&init_task);
+ cprm.file = file_open_root(root.dentry, root.mnt,
+ cn.corename, open_flags, 0600);
+ path_put(&root);
+ } else {
+ cprm.file = filp_open(cn.corename, open_flags, 0600);
+ }
if (IS_ERR(cprm.file))
goto fail_unlock;
git.openpandora.org / pandora-kernel.git / blobdiff