From ab8cd295b635634689825cf7dd9a5ace4009f497 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Tue, 8 Jun 2021 15:22:02 +0200 Subject: [PATCH] 4.9-stable patches added patches: pid-take-a-reference-when-initializing-cad_pid.patch --- ...-reference-when-initializing-cad_pid.patch | 138 ++++++++++++++++++ queue-4.9/series | 1 + 2 files changed, 139 insertions(+) create mode 100644 queue-4.9/pid-take-a-reference-when-initializing-cad_pid.patch diff --git a/queue-4.9/pid-take-a-reference-when-initializing-cad_pid.patch b/queue-4.9/pid-take-a-reference-when-initializing-cad_pid.patch new file mode 100644 index 00000000000..a11af581dc0 --- /dev/null +++ b/queue-4.9/pid-take-a-reference-when-initializing-cad_pid.patch @@ -0,0 +1,138 @@ +From 0711f0d7050b9e07c44bc159bbc64ac0a1022c7f Mon Sep 17 00:00:00 2001 +From: Mark Rutland +Date: Fri, 4 Jun 2021 20:01:14 -0700 +Subject: pid: take a reference when initializing `cad_pid` + +From: Mark Rutland + +commit 0711f0d7050b9e07c44bc159bbc64ac0a1022c7f upstream. + +During boot, kernel_init_freeable() initializes `cad_pid` to the init +task's struct pid. Later on, we may change `cad_pid` via a sysctl, and +when this happens proc_do_cad_pid() will increment the refcount on the +new pid via get_pid(), and will decrement the refcount on the old pid +via put_pid(). As we never called get_pid() when we initialized +`cad_pid`, we decrement a reference we never incremented, can therefore +free the init task's struct pid early. As there can be dangling +references to the struct pid, we can later encounter a use-after-free +(e.g. when delivering signals). + +This was spotted when fuzzing v5.13-rc3 with Syzkaller, but seems to +have been around since the conversion of `cad_pid` to struct pid in +commit 9ec52099e4b8 ("[PATCH] replace cad_pid by a struct pid") from the +pre-KASAN stone age of v2.6.19. + +Fix this by getting a reference to the init task's struct pid when we +assign it to `cad_pid`. + +Full KASAN splat below. + + ================================================================== + BUG: KASAN: use-after-free in ns_of_pid include/linux/pid.h:153 [inline] + BUG: KASAN: use-after-free in task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509 + Read of size 4 at addr ffff23794dda0004 by task syz-executor.0/273 + + CPU: 1 PID: 273 Comm: syz-executor.0 Not tainted 5.12.0-00001-g9aef892b2d15 #1 + Hardware name: linux,dummy-virt (DT) + Call trace: + ns_of_pid include/linux/pid.h:153 [inline] + task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509 + do_notify_parent+0x308/0xe60 kernel/signal.c:1950 + exit_notify kernel/exit.c:682 [inline] + do_exit+0x2334/0x2bd0 kernel/exit.c:845 + do_group_exit+0x108/0x2c8 kernel/exit.c:922 + get_signal+0x4e4/0x2a88 kernel/signal.c:2781 + do_signal arch/arm64/kernel/signal.c:882 [inline] + do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936 + work_pending+0xc/0x2dc + + Allocated by task 0: + slab_post_alloc_hook+0x50/0x5c0 mm/slab.h:516 + slab_alloc_node mm/slub.c:2907 [inline] + slab_alloc mm/slub.c:2915 [inline] + kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920 + alloc_pid+0xdc/0xc00 kernel/pid.c:180 + copy_process+0x2794/0x5e18 kernel/fork.c:2129 + kernel_clone+0x194/0x13c8 kernel/fork.c:2500 + kernel_thread+0xd4/0x110 kernel/fork.c:2552 + rest_init+0x44/0x4a0 init/main.c:687 + arch_call_rest_init+0x1c/0x28 + start_kernel+0x520/0x554 init/main.c:1064 + 0x0 + + Freed by task 270: + slab_free_hook mm/slub.c:1562 [inline] + slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600 + slab_free mm/slub.c:3161 [inline] + kmem_cache_free+0x224/0x8e0 mm/slub.c:3177 + put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114 + put_pid+0x30/0x48 kernel/pid.c:109 + proc_do_cad_pid+0x190/0x1b0 kernel/sysctl.c:1401 + proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591 + proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617 + call_write_iter include/linux/fs.h:1977 [inline] + new_sync_write+0x3ac/0x510 fs/read_write.c:518 + vfs_write fs/read_write.c:605 [inline] + vfs_write+0x9c4/0x1018 fs/read_write.c:585 + ksys_write+0x124/0x240 fs/read_write.c:658 + __do_sys_write fs/read_write.c:670 [inline] + __se_sys_write fs/read_write.c:667 [inline] + __arm64_sys_write+0x78/0xb0 fs/read_write.c:667 + __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline] + invoke_syscall arch/arm64/kernel/syscall.c:49 [inline] + el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129 + do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168 + el0_svc+0x28/0x38 arch/arm64/kernel/entry-common.c:416 + el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432 + el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701 + + The buggy address belongs to the object at ffff23794dda0000 + which belongs to the cache pid of size 224 + The buggy address is located 4 bytes inside of + 224-byte region [ffff23794dda0000, ffff23794dda00e0) + The buggy address belongs to the page: + page:(____ptrval____) refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4dda0 + head:(____ptrval____) order:1 compound_mapcount:0 + flags: 0x3fffc0000010200(slab|head) + raw: 03fffc0000010200 dead000000000100 dead000000000122 ffff23794d40d080 + raw: 0000000000000000 0000000000190019 00000001ffffffff 0000000000000000 + page dumped because: kasan: bad access detected + + Memory state around the buggy address: + ffff23794dd9ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc + ffff23794dd9ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc + >ffff23794dda0000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb + ^ + ffff23794dda0080: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc + ffff23794dda0100: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00 + ================================================================== + +Link: https://lkml.kernel.org/r/20210524172230.38715-1-mark.rutland@arm.com +Fixes: 9ec52099e4b8678a ("[PATCH] replace cad_pid by a struct pid") +Signed-off-by: Mark Rutland +Acked-by: Christian Brauner +Cc: Cedric Le Goater +Cc: Christian Brauner +Cc: Eric W. Biederman +Cc: Kees Cook +Cc: Paul Mackerras +Cc: +Signed-off-by: Andrew Morton +Signed-off-by: Linus Torvalds +Signed-off-by: Greg Kroah-Hartman +--- + init/main.c | 2 +- + 1 file changed, 1 insertion(+), 1 deletion(-) + +--- a/init/main.c ++++ b/init/main.c +@@ -1005,7 +1005,7 @@ static noinline void __init kernel_init_ + */ + set_cpus_allowed_ptr(current, cpu_all_mask); + +- cad_pid = task_pid(current); ++ cad_pid = get_pid(task_pid(current)); + + smp_prepare_cpus(setup_max_cpus); + diff --git a/queue-4.9/series b/queue-4.9/series index eff7ce2e064..3c3393c2c7b 100644 --- a/queue-4.9/series +++ b/queue-4.9/series @@ -18,3 +18,4 @@ net-caif-fix-memory-leak-in-caif_device_notify.patch net-caif-fix-memory-leak-in-cfusbl_device_notify.patch alsa-timer-fix-master-timer-notification.patch ext4-fix-bug-on-in-ext4_es_cache_extent-as-ext4_split_extent_at-failed.patch +pid-take-a-reference-when-initializing-cad_pid.patch -- 2.47.3