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android: drivers: Avoid debugfs race in binder

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If a /d/binder/proc/[pid] entry is kept open after linux has
torn down the associated process, binder_proc_show can deference
an invalid binder_proc that has been stashed in the debugfs
inode.  Validate that the binder_proc ptr passed into binder_proc_show
has not been freed by looking for it within the global process list
whilst the global lock is held. If the ptr is not valid, print nothing.

Cc: Colin Cross <ccross@android.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Dmitry Shmidt <dimitrysh@google.com>
Cc: Rom Lemarchand <romlem@google.com>
Cc: Serban Constantinescu <serban.constantinescu@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
[jstultz: Minor commit message tweaks]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Riley Andrews 2016-02-09 21:05:33 -08:00 committed by Greg Kroah-Hartman
parent 212265e5ad
commit 83050a4e21
1 changed files with 13 additions and 2 deletions
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15
drivers/android/binder.c
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@ -3600,13 +3600,24 @@ static int binder_transactions_show(struct seq_file *m, void *unused)
static int binder_proc_show(struct seq_file *m, void *unused)
{
struct binder_proc *itr;
struct binder_proc *proc = m->private;
int do_lock = !binder_debug_no_lock;
bool valid_proc = false;
if (do_lock)
binder_lock(__func__);
seq_puts(m, "binder proc state:\n");
print_binder_proc(m, proc, 1);
hlist_for_each_entry(itr, &binder_procs, proc_node) {
if (itr == proc) {
valid_proc = true;
break;
}
}
if (valid_proc) {
seq_puts(m, "binder proc state:\n");
print_binder_proc(m, proc, 1);
}
if (do_lock)
binder_unlock(__func__);
return 0;