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procfs: mem permission cleanup 

This cleans up the permission checks done for /proc/PID/mem i/o calls.  It
puts all the logic in a new function, check_mem_permission().

The old code repeated the (!MAY_PTRACE(task) || !ptrace_may_attach(task))
magical expression multiple times.  The new function does all that work in one
place, with clear comments.

The old code called security_ptrace() twice on successful checks, once in
MAY_PTRACE() and once in __ptrace_may_attach().  Now it's only called once,
and only if all other checks have succeeded.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2008-04-29 01:01:38 -07:00 committed by Linus Torvalds
parent 0d5c9f5f59
commit 638fa202cd
1 changed files with 29 additions and 9 deletions
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38
fs/proc/base.c
View File

@ -195,12 +195,32 @@ static int proc_root_link(struct inode *inode, struct path *path)
return result;
}
#define MAY_PTRACE(task) \
(task == current || \
(task->parent == current && \
(task->ptrace & PT_PTRACED) && \
(task_is_stopped_or_traced(task)) && \
security_ptrace(current,task) == 0))
/*
* Return zero if current may access user memory in @task, -error if not.
*/
static int check_mem_permission(struct task_struct *task)
{
/*
* A task can always look at itself, in case it chooses
* to use system calls instead of load instructions.
*/
if (task == current)
return 0;
/*
* If current is actively ptrace'ing, and would also be
* permitted to freshly attach with ptrace now, permit it.
*/
if (task->parent == current && (task->ptrace & PT_PTRACED) &&
task_is_stopped_or_traced(task) &&
ptrace_may_attach(task))
return 0;
/*
* Noone else is allowed.
*/
return -EPERM;
}
struct mm_struct *mm_for_maps(struct task_struct *task)
{
@ -722,7 +742,7 @@ static ssize_t mem_read(struct file * file, char __user * buf,
if (!task)
goto out_no_task;
if (!MAY_PTRACE(task) || !ptrace_may_attach(task))
if (check_mem_permission(task))
goto out;
ret = -ENOMEM;
@ -748,7 +768,7 @@ static ssize_t mem_read(struct file * file, char __user * buf,
this_len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
retval = access_process_vm(task, src, page, this_len, 0);
if (!retval || !MAY_PTRACE(task) || !ptrace_may_attach(task)) {
if (!retval || check_mem_permission(task)) {
if (!ret)
ret = -EIO;
break;
@ -792,7 +812,7 @@ static ssize_t mem_write(struct file * file, const char __user *buf,
if (!task)
goto out_no_task;
if (!MAY_PTRACE(task) || !ptrace_may_attach(task))
if (check_mem_permission(task))
goto out;
copied = -ENOMEM;