4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Li RongQing lirongqing@baidu.com
[ Upstream commit 6d2b0f02f5a07a4bf02e4cbc90d7eaa85cac2986 ]
proc_exit_connector() uses ->real_parent lockless. This is not safe that its parent can go away at any moment, so use RCU to protect it, and ensure that this task is not released.
[ 747.624551] ================================================================== [ 747.632946] BUG: KASAN: use-after-free in proc_exit_connector+0x1f7/0x310 [ 747.640686] Read of size 4 at addr ffff88a0276988e0 by task sshd/2882 [ 747.648032] [ 747.649804] CPU: 11 PID: 2882 Comm: sshd Tainted: G E 4.19.26-rc2 #11 [ 747.658629] Hardware name: IBM x3550M4 -[7914OFV]-/00AM544, BIOS -[D7E142BUS-1.71]- 07/31/2014 [ 747.668419] Call Trace: [ 747.671269] dump_stack+0xf0/0x19b [ 747.675186] ? show_regs_print_info+0x5/0x5 [ 747.679988] ? kmsg_dump_rewind_nolock+0x59/0x59 [ 747.685302] print_address_description+0x6a/0x270 [ 747.691162] kasan_report+0x258/0x380 [ 747.695835] ? proc_exit_connector+0x1f7/0x310 [ 747.701402] proc_exit_connector+0x1f7/0x310 [ 747.706767] ? proc_coredump_connector+0x2d0/0x2d0 [ 747.712715] ? _raw_write_unlock_irq+0x29/0x50 [ 747.718270] ? _raw_write_unlock_irq+0x29/0x50 [ 747.723820] ? ___preempt_schedule+0x16/0x18 [ 747.729193] ? ___preempt_schedule+0x16/0x18 [ 747.734574] do_exit+0xa11/0x14f0 [ 747.738880] ? mm_update_next_owner+0x590/0x590 [ 747.744525] ? debug_show_all_locks+0x3c0/0x3c0 [ 747.761448] ? ktime_get_coarse_real_ts64+0xeb/0x1c0 [ 747.767589] ? lockdep_hardirqs_on+0x1a6/0x290 [ 747.773154] ? check_chain_key+0x139/0x1f0 [ 747.778345] ? check_flags.part.35+0x240/0x240 [ 747.783908] ? __lock_acquire+0x2300/0x2300 [ 747.789171] ? _raw_spin_unlock_irqrestore+0x59/0x70 [ 747.795316] ? _raw_spin_unlock_irqrestore+0x59/0x70 [ 747.801457] ? do_raw_spin_unlock+0x10f/0x1e0 [ 747.806914] ? do_raw_spin_trylock+0x120/0x120 [ 747.812481] ? preempt_count_sub+0x14/0xc0 [ 747.817645] ? _raw_spin_unlock+0x2e/0x50 [ 747.822708] ? __handle_mm_fault+0x12db/0x1fa0 [ 747.828367] ? __pmd_alloc+0x2d0/0x2d0 [ 747.833143] ? check_noncircular+0x50/0x50 [ 747.838309] ? match_held_lock+0x7f/0x340 [ 747.843380] ? check_noncircular+0x50/0x50 [ 747.848561] ? handle_mm_fault+0x21a/0x5f0 [ 747.853730] ? check_flags.part.35+0x240/0x240 [ 747.859290] ? check_chain_key+0x139/0x1f0 [ 747.864474] ? __do_page_fault+0x40f/0x760 [ 747.869655] ? __audit_syscall_entry+0x4b/0x1f0 [ 747.875319] ? syscall_trace_enter+0x1d5/0x7b0 [ 747.880877] ? trace_raw_output_preemptirq_template+0x90/0x90 [ 747.887895] ? trace_raw_output_sys_exit+0x80/0x80 [ 747.893860] ? up_read+0x3b/0x90 [ 747.898142] ? stop_critical_timings+0x260/0x260 [ 747.903909] do_group_exit+0xe0/0x1c0 [ 747.908591] ? __x64_sys_exit+0x30/0x30 [ 747.913460] ? trace_raw_output_preemptirq_template+0x90/0x90 [ 747.920485] ? tracer_hardirqs_on+0x270/0x270 [ 747.925956] __x64_sys_exit_group+0x28/0x30 [ 747.931214] do_syscall_64+0x117/0x400 [ 747.935988] ? syscall_return_slowpath+0x2f0/0x2f0 [ 747.941931] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 747.947788] ? trace_hardirqs_on_caller+0x1d0/0x1d0 [ 747.953838] ? lockdep_sys_exit+0x16/0x8e [ 747.958915] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 747.964784] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 747.971021] RIP: 0033:0x7f572f154c68 [ 747.975606] Code: Bad RIP value. [ 747.979791] RSP: 002b:00007ffed2dfaa58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 [ 747.989324] RAX: ffffffffffffffda RBX: 00007f572f431840 RCX: 00007f572f154c68 [ 747.997910] RDX: 0000000000000001 RSI: 000000000000003c RDI: 0000000000000001 [ 748.006495] RBP: 0000000000000001 R08: 00000000000000e7 R09: fffffffffffffee0 [ 748.015079] R10: 00007f572f4387e8 R11: 0000000000000246 R12: 00007f572f431840 [ 748.023664] R13: 000055a7f90f2c50 R14: 000055a7f96e2310 R15: 000055a7f96e2310 [ 748.032287] [ 748.034509] Allocated by task 2300: [ 748.038982] kasan_kmalloc+0xa0/0xd0 [ 748.043562] kmem_cache_alloc_node+0xf5/0x2e0 [ 748.049018] copy_process+0x1781/0x4790 [ 748.053884] _do_fork+0x166/0x9a0 [ 748.058163] do_syscall_64+0x117/0x400 [ 748.062943] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 748.069180] [ 748.071405] Freed by task 15395: [ 748.075591] __kasan_slab_free+0x130/0x180 [ 748.080752] kmem_cache_free+0xc2/0x310 [ 748.085619] free_task+0xea/0x130 [ 748.089901] __put_task_struct+0x177/0x230 [ 748.095063] finish_task_switch+0x51b/0x5d0 [ 748.100315] __schedule+0x506/0xfa0 [ 748.104791] schedule+0xca/0x260 [ 748.108978] futex_wait_queue_me+0x27e/0x420 [ 748.114333] futex_wait+0x251/0x550 [ 748.118814] do_futex+0x75b/0xf80 [ 748.123097] __x64_sys_futex+0x231/0x2a0 [ 748.128065] do_syscall_64+0x117/0x400 [ 748.132835] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 748.139066] [ 748.141289] The buggy address belongs to the object at ffff88a027698000 [ 748.141289] which belongs to the cache task_struct of size 12160 [ 748.156589] The buggy address is located 2272 bytes inside of [ 748.156589] 12160-byte region [ffff88a027698000, ffff88a02769af80) [ 748.171114] The buggy address belongs to the page: [ 748.177055] page:ffffea00809da600 count:1 mapcount:0 mapping:ffff888107d01e00 index:0x0 compound_mapcount: 0 [ 748.189136] flags: 0x57ffffc0008100(slab|head) [ 748.194688] raw: 0057ffffc0008100 ffffea00809a3200 0000000300000003 ffff888107d01e00 [ 748.204424] raw: 0000000000000000 0000000000020002 00000001ffffffff 0000000000000000 [ 748.214146] page dumped because: kasan: bad access detected [ 748.220976] [ 748.223197] Memory state around the buggy address: [ 748.229128] ffff88a027698780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 748.238271] ffff88a027698800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 748.247414] >ffff88a027698880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 748.256564] ^ [ 748.264267] ffff88a027698900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 748.273493] ffff88a027698980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 748.282630] ==================================================================
Fixes: b086ff87251b4a4 ("connector: add parent pid and tgid to coredump and exit events") Signed-off-by: Zhang Yu zhangyu31@baidu.com Signed-off-by: Li RongQing lirongqing@baidu.com Acked-by: Evgeniy Polyakov zbr@ioremap.net Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/connector/cn_proc.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-)
--- a/drivers/connector/cn_proc.c +++ b/drivers/connector/cn_proc.c @@ -250,6 +250,7 @@ void proc_coredump_connector(struct task { struct cn_msg *msg; struct proc_event *ev; + struct task_struct *parent; __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
if (atomic_read(&proc_event_num_listeners) < 1) @@ -262,8 +263,14 @@ void proc_coredump_connector(struct task ev->what = PROC_EVENT_COREDUMP; ev->event_data.coredump.process_pid = task->pid; ev->event_data.coredump.process_tgid = task->tgid; - ev->event_data.coredump.parent_pid = task->real_parent->pid; - ev->event_data.coredump.parent_tgid = task->real_parent->tgid; + + rcu_read_lock(); + if (pid_alive(task)) { + parent = rcu_dereference(task->real_parent); + ev->event_data.coredump.parent_pid = parent->pid; + ev->event_data.coredump.parent_tgid = parent->tgid; + } + rcu_read_unlock();
memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id)); msg->ack = 0; /* not used */ @@ -276,6 +283,7 @@ void proc_exit_connector(struct task_str { struct cn_msg *msg; struct proc_event *ev; + struct task_struct *parent; __u8 buffer[CN_PROC_MSG_SIZE] __aligned(8);
if (atomic_read(&proc_event_num_listeners) < 1) @@ -290,8 +298,14 @@ void proc_exit_connector(struct task_str ev->event_data.exit.process_tgid = task->tgid; ev->event_data.exit.exit_code = task->exit_code; ev->event_data.exit.exit_signal = task->exit_signal; - ev->event_data.exit.parent_pid = task->real_parent->pid; - ev->event_data.exit.parent_tgid = task->real_parent->tgid; + + rcu_read_lock(); + if (pid_alive(task)) { + parent = rcu_dereference(task->real_parent); + ev->event_data.exit.parent_pid = parent->pid; + ev->event_data.exit.parent_tgid = parent->tgid; + } + rcu_read_unlock();
memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id)); msg->ack = 0; /* not used */