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authorRoland McGrath <roland@redhat.com>2008-04-29 01:01:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-29 08:06:17 -0700
commit638fa202cdb207083a12d6f73e313605a8fc1037 (patch)
treee049d74e9f7e15a55149dc17482572c8b2aefa18 /fs
parent0d5c9f5f59a61cf8e98e2925cb5d81cbe7694305 (diff)
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>
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/base.c38
1 files changed, 29 insertions, 9 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index b48ddb119945..fcf02f2deeba 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -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;