diff options
| author | Adrian Salido <salidoa@google.com> | 2016-12-01 18:07:42 -0800 |
|---|---|---|
| committer | Joey Rizzoli <joey@lineageos.org> | 2017-06-14 23:00:20 +0200 |
| commit | f3da5c19bdd2b20846be6c19107e68bf5556b6a8 (patch) | |
| tree | e6bf6ae436944bba4384a5abd9621843cd1ac380 | |
| parent | 9936cd0d736e7ebee1376e8417c9791e969b0e89 (diff) | |
fs/proc/array.c: make safe access to group_leader
As mentioned in commit 52ee2dfdd4f51cf422ea6a96a0846dc94244aa37
("pids: refactor vnr/nr_ns helpers to make them safe"). *_nr_ns
helpers used to be buggy. The commit addresses most of the helpers but
is missing task_tgid_xxx()
Without this protection there is a possible use after free reported by
kasan instrumented kernel:
==================================================================
BUG: KASAN: use-after-free in task_tgid_nr_ns+0x2c/0x44 at addr ***
Read of size 8 by task cat/2472
CPU: 1 PID: 2472 Comm: cat Tainted: ****
Hardware name: Google Tegra210 Smaug Rev 1,3+ (DT)
Call trace:
[<ffffffc00020ad2c>] dump_backtrace+0x0/0x17c
[<ffffffc00020aec0>] show_stack+0x18/0x24
[<ffffffc0011573d0>] dump_stack+0x94/0x100
[<ffffffc0003c7dc0>] kasan_report+0x308/0x554
[<ffffffc0003c7518>] __asan_load8+0x20/0x7c
[<ffffffc00025a54c>] task_tgid_nr_ns+0x28/0x44
[<ffffffc00046951c>] proc_pid_status+0x444/0x1080
[<ffffffc000460f60>] proc_single_show+0x8c/0xdc
[<ffffffc0004081b0>] seq_read+0x2e8/0x6f0
[<ffffffc0003d1420>] vfs_read+0xd8/0x1e0
[<ffffffc0003d1b98>] SyS_read+0x68/0xd4
Accessing group_leader while holding rcu_lock and using the now safe
helpers introduced in the commit mentioned, this race condition is
addressed.
Signed-off-by: Adrian Salido <salidoa@google.com>
Change-Id: I4315217922dda375a30a3581c0c1740dda7b531b
Bug: 31495866
| -rw-r--r-- | fs/proc/array.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/fs/proc/array.c b/fs/proc/array.c index e7bb0fed720..607f80c8d50 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -166,16 +166,16 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns, int g; struct fdtable *fdt = NULL; const struct cred *cred; - pid_t ppid, tpid; + pid_t ppid = 0, tpid = 0; + struct task_struct *leader = NULL; rcu_read_lock(); - ppid = pid_alive(p) ? - task_tgid_nr_ns(rcu_dereference(p->real_parent), ns) : 0; - tpid = 0; if (pid_alive(p)) { struct task_struct *tracer = ptrace_parent(p); if (tracer) tpid = task_pid_nr_ns(tracer, ns); + ppid = task_tgid_nr_ns(rcu_dereference(p->real_parent), ns); + leader = p->group_leader; } cred = get_task_cred(p); seq_printf(m, @@ -187,7 +187,7 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns, "Uid:\t%d\t%d\t%d\t%d\n" "Gid:\t%d\t%d\t%d\t%d\n", get_task_state(p), - task_tgid_nr_ns(p, ns), + leader ? task_pid_nr_ns(leader, ns) : 0, pid_nr_ns(pid, ns), ppid, tpid, cred->uid, cred->euid, cred->suid, cred->fsuid, |