CVE-2012-0056 proc: clean up and fix /proc/<pid>/mem (rhbz 782681)
This commit is contained in:
Josh Boyer
parent
d283b6f1bb
commit
3b621a2d6e
@ -764,6 +764,9 @@ Patch21074: KVM-x86-fix-missing-checks-in-syscall-emulation.patch
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#rhbz 728740
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Patch21076: rtl8192cu-Fix-WARNING-on-suspend-resume.patch
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#rhbz 782681
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Patch21085: proc-clean-up-and-fix-proc-pid-mem-handling.patch
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# compat-wireless patches
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Patch50000: compat-wireless-config-fixups.patch
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Patch50001: compat-wireless-pr_fmt-warning-avoidance.patch
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@ -1484,6 +1487,9 @@ ApplyPatch KVM-x86-fix-missing-checks-in-syscall-emulation.patch
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#rhbz 728740
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ApplyPatch rtl8192cu-Fix-WARNING-on-suspend-resume.patch
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#rhbz 782681
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ApplyPatch proc-clean-up-and-fix-proc-pid-mem-handling.patch
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# END OF PATCH APPLICATIONS
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%endif
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@ -2322,6 +2328,9 @@ fi
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# ||----w |
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# || ||
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%changelog
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* Wed Jan 18 2012 Josh Boyer <jwboyer@redhat.com>
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- CVE-2012-0056 proc: clean up and fix /proc/<pid>/mem (rhbz 782681)
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* Tue Jan 17 2012 Dave Jones <davej@redhat.com>
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- Rawhide builds now use MAXSMP on x86.
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- For release builds, set x86-64 to support 64 CPUs.
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268
proc-clean-up-and-fix-proc-pid-mem-handling.patch
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268
proc-clean-up-and-fix-proc-pid-mem-handling.patch
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@ -0,0 +1,268 @@
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From e268337dfe26dfc7efd422a804dbb27977a3cccc Mon Sep 17 00:00:00 2001
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From: Linus Torvalds <torvalds@linux-foundation.org>
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Date: Tue, 17 Jan 2012 15:21:19 -0800
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Subject: [PATCH] proc: clean up and fix /proc/<pid>/mem handling
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Jüri Aedla reported that the /proc/<pid>/mem handling really isn't very
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robust, and it also doesn't match the permission checking of any of the
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other related files.
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This changes it to do the permission checks at open time, and instead of
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tracking the process, it tracks the VM at the time of the open. That
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simplifies the code a lot, but does mean that if you hold the file
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descriptor open over an execve(), you'll continue to read from the _old_
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VM.
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That is different from our previous behavior, but much simpler. If
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somebody actually finds a load where this matters, we'll need to revert
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this commit.
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I suspect that nobody will ever notice - because the process mapping
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addresses will also have changed as part of the execve. So you cannot
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actually usefully access the fd across a VM change simply because all
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the offsets for IO would have changed too.
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Reported-by: Jüri Aedla <asd@ut.ee>
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Cc: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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fs/proc/base.c | 145 +++++++++++++++-----------------------------------------
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1 files changed, 39 insertions(+), 106 deletions(-)
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diff --git a/fs/proc/base.c b/fs/proc/base.c
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index 5485a53..662ddf2 100644
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--- a/fs/proc/base.c
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+++ b/fs/proc/base.c
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@@ -198,65 +198,7 @@ static int proc_root_link(struct dentry *dentry, struct path *path)
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return result;
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}
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-static struct mm_struct *__check_mem_permission(struct task_struct *task)
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-{
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- struct mm_struct *mm;
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-
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- mm = get_task_mm(task);
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- if (!mm)
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- return ERR_PTR(-EINVAL);
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-
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- /*
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- * A task can always look at itself, in case it chooses
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- * to use system calls instead of load instructions.
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- */
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- if (task == current)
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- return mm;
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-
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- /*
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- * If current is actively ptrace'ing, and would also be
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- * permitted to freshly attach with ptrace now, permit it.
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- */
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- if (task_is_stopped_or_traced(task)) {
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- int match;
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- rcu_read_lock();
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- match = (ptrace_parent(task) == current);
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- rcu_read_unlock();
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- if (match && ptrace_may_access(task, PTRACE_MODE_ATTACH))
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- return mm;
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- }
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-
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- /*
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- * No one else is allowed.
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- */
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- mmput(mm);
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- return ERR_PTR(-EPERM);
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-}
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-
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-/*
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- * If current may access user memory in @task return a reference to the
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- * corresponding mm, otherwise ERR_PTR.
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- */
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-static struct mm_struct *check_mem_permission(struct task_struct *task)
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-{
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- struct mm_struct *mm;
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- int err;
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-
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- /*
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- * Avoid racing if task exec's as we might get a new mm but validate
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- * against old credentials.
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- */
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- err = mutex_lock_killable(&task->signal->cred_guard_mutex);
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- if (err)
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- return ERR_PTR(err);
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-
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- mm = __check_mem_permission(task);
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- mutex_unlock(&task->signal->cred_guard_mutex);
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-
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- return mm;
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-}
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-
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-struct mm_struct *mm_for_maps(struct task_struct *task)
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+static struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
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{
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struct mm_struct *mm;
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int err;
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@@ -267,7 +209,7 @@ struct mm_struct *mm_for_maps(struct task_struct *task)
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mm = get_task_mm(task);
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if (mm && mm != current->mm &&
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- !ptrace_may_access(task, PTRACE_MODE_READ)) {
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+ !ptrace_may_access(task, mode)) {
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mmput(mm);
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mm = ERR_PTR(-EACCES);
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}
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@@ -276,6 +218,11 @@ struct mm_struct *mm_for_maps(struct task_struct *task)
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return mm;
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}
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+struct mm_struct *mm_for_maps(struct task_struct *task)
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+{
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+ return mm_access(task, PTRACE_MODE_READ);
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+}
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+
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static int proc_pid_cmdline(struct task_struct *task, char * buffer)
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{
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int res = 0;
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@@ -752,38 +699,39 @@ static const struct file_operations proc_single_file_operations = {
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static int mem_open(struct inode* inode, struct file* file)
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{
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- file->private_data = (void*)((long)current->self_exec_id);
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+ struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
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+ struct mm_struct *mm;
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+
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+ if (!task)
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+ return -ESRCH;
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+
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+ mm = mm_access(task, PTRACE_MODE_ATTACH);
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+ put_task_struct(task);
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+
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+ if (IS_ERR(mm))
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+ return PTR_ERR(mm);
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+
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/* OK to pass negative loff_t, we can catch out-of-range */
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file->f_mode |= FMODE_UNSIGNED_OFFSET;
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+ file->private_data = mm;
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+
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return 0;
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}
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static ssize_t mem_read(struct file * file, char __user * buf,
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size_t count, loff_t *ppos)
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{
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- struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
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+ int ret;
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char *page;
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unsigned long src = *ppos;
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- int ret = -ESRCH;
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- struct mm_struct *mm;
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+ struct mm_struct *mm = file->private_data;
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- if (!task)
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- goto out_no_task;
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+ if (!mm)
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+ return 0;
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- ret = -ENOMEM;
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page = (char *)__get_free_page(GFP_TEMPORARY);
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if (!page)
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- goto out;
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-
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- mm = check_mem_permission(task);
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- ret = PTR_ERR(mm);
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- if (IS_ERR(mm))
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- goto out_free;
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-
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- ret = -EIO;
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-
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- if (file->private_data != (void*)((long)current->self_exec_id))
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- goto out_put;
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+ return -ENOMEM;
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ret = 0;
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@@ -810,13 +758,7 @@ static ssize_t mem_read(struct file * file, char __user * buf,
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}
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*ppos = src;
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-out_put:
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- mmput(mm);
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-out_free:
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free_page((unsigned long) page);
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-out:
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- put_task_struct(task);
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-out_no_task:
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return ret;
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}
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@@ -825,27 +767,15 @@ static ssize_t mem_write(struct file * file, const char __user *buf,
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{
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int copied;
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char *page;
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- struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
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unsigned long dst = *ppos;
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- struct mm_struct *mm;
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+ struct mm_struct *mm = file->private_data;
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- copied = -ESRCH;
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- if (!task)
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- goto out_no_task;
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+ if (!mm)
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+ return 0;
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- copied = -ENOMEM;
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page = (char *)__get_free_page(GFP_TEMPORARY);
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if (!page)
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- goto out_task;
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-
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- mm = check_mem_permission(task);
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- copied = PTR_ERR(mm);
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- if (IS_ERR(mm))
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- goto out_free;
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-
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- copied = -EIO;
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- if (file->private_data != (void *)((long)current->self_exec_id))
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- goto out_mm;
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+ return -ENOMEM;
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copied = 0;
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while (count > 0) {
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@@ -869,13 +799,7 @@ static ssize_t mem_write(struct file * file, const char __user *buf,
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}
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*ppos = dst;
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-out_mm:
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- mmput(mm);
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-out_free:
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free_page((unsigned long) page);
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-out_task:
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- put_task_struct(task);
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-out_no_task:
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return copied;
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}
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@@ -895,11 +819,20 @@ loff_t mem_lseek(struct file *file, loff_t offset, int orig)
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return file->f_pos;
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}
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+static int mem_release(struct inode *inode, struct file *file)
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+{
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+ struct mm_struct *mm = file->private_data;
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+
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+ mmput(mm);
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+ return 0;
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+}
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+
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static const struct file_operations proc_mem_operations = {
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.llseek = mem_lseek,
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.read = mem_read,
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.write = mem_write,
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.open = mem_open,
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+ .release = mem_release,
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};
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static ssize_t environ_read(struct file *file, char __user *buf,
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--
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1.7.7.5
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