Re: [PATCH stable<3.18 1/1] proc: Fix ptrace-based permission checks for accessing task maps

From: Jiri Slaby
Date: Sun Feb 28 2016 - 05:00:58 EST


CCing ptrace guys.

I would appreciate if somebody could ACK this.

On 02/28/2016, 09:42 AM, Corey Wright wrote:
> Modify mm_access() calls in fs/proc/task_mmu.c and fs/proc/task_nommu.c to
> have the mode include PTRACE_MODE_FSCREDS so accessing /proc/pid/maps and
> /proc/pid/pagemap is not denied to all users.
>
> In backporting upstream commit caaee623 to pre-3.18 kernel versions it was
> overlooked that mm_access() is used in fs/proc/task_*mmu.c as those calls
> were removed in 3.18 (by upstream commit 29a40ace) and did not exist at the
> time of the original commit.
>
> Signed-off-by: Corey Wright <undefined@xxxxxxxxx>
> Cc: Jann Horn <jann@xxxxxxxxx>
> ---
> fs/proc/task_mmu.c | 4 ++--
> fs/proc/task_nommu.c | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 9f285fb..b86db12 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -170,7 +170,7 @@ static void *m_start(struct seq_file *m, loff_t *pos)
> if (!priv->task)
> return ERR_PTR(-ESRCH);
>
> - mm = mm_access(priv->task, PTRACE_MODE_READ);
> + mm = mm_access(priv->task, PTRACE_MODE_READ_FSCREDS);
> if (!mm || IS_ERR(mm))
> return mm;
> down_read(&mm->mmap_sem);
> @@ -1044,7 +1044,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
> if (!pm.buffer)
> goto out_task;
>
> - mm = mm_access(task, PTRACE_MODE_READ);
> + mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
> ret = PTR_ERR(mm);
> if (!mm || IS_ERR(mm))
> goto out_free;
> diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
> index 56123a6..123c198 100644
> --- a/fs/proc/task_nommu.c
> +++ b/fs/proc/task_nommu.c
> @@ -223,7 +223,7 @@ static void *m_start(struct seq_file *m, loff_t *pos)
> if (!priv->task)
> return ERR_PTR(-ESRCH);
>
> - mm = mm_access(priv->task, PTRACE_MODE_READ);
> + mm = mm_access(priv->task, PTRACE_MODE_READ_FSCREDS);
> if (!mm || IS_ERR(mm)) {
> put_task_struct(priv->task);
> priv->task = NULL;
>


--
js
suse labs