Re: [PATCH AUTOSEL 6.3] mailbox: mailbox-test: Fix potential double-free in mbox_test_message_write()

On Fri, 19 May 2023, Sasha Levin wrote:

From: Lee Jones lee@kernel.org

[ Upstream commit 2d1e952a2b8e5e92d8d55ac88a7cf7ca5ea591ad ]

If a user can make copy_from_user() fail, there is a potential for UAF/DF due to a lack of locking around the allocation, use and freeing of the data buffers.

This issue is not theoretical. I managed to author a POC for it:

BUG: KASAN: double-free in kfree+0x5c/0xac
Free of addr ffff29280be5de00 by task poc/356
CPU: 1 PID: 356 Comm: poc Not tainted 6.1.0-00001-g961aa6552c04-dirty #20
Hardware name: linux,dummy-virt (DT)
Call trace:
 dump_backtrace.part.0+0xe0/0xf0
 show_stack+0x18/0x40
 dump_stack_lvl+0x64/0x80
 print_report+0x188/0x48c
 kasan_report_invalid_free+0xa0/0xc0
 ____kasan_slab_free+0x174/0x1b0
 __kasan_slab_free+0x18/0x24
 __kmem_cache_free+0x130/0x2e0
 kfree+0x5c/0xac
 mbox_test_message_write+0x208/0x29c
 full_proxy_write+0x90/0xf0
 vfs_write+0x154/0x440
 ksys_write+0xcc/0x180
 __arm64_sys_write+0x44/0x60
 invoke_syscall+0x60/0x190
 el0_svc_common.constprop.0+0x7c/0x160
 do_el0_svc+0x40/0xf0
 el0_svc+0x2c/0x6c
 el0t_64_sync_handler+0xf4/0x120
 el0t_64_sync+0x18c/0x190

Allocated by task 356:
 kasan_save_stack+0x3c/0x70
 kasan_set_track+0x2c/0x40
 kasan_save_alloc_info+0x24/0x34
 __kasan_kmalloc+0xb8/0xc0
 kmalloc_trace+0x58/0x70
 mbox_test_message_write+0x6c/0x29c
 full_proxy_write+0x90/0xf0
 vfs_write+0x154/0x440
 ksys_write+0xcc/0x180
 __arm64_sys_write+0x44/0x60
 invoke_syscall+0x60/0x190
 el0_svc_common.constprop.0+0x7c/0x160
 do_el0_svc+0x40/0xf0
 el0_svc+0x2c/0x6c
 el0t_64_sync_handler+0xf4/0x120
 el0t_64_sync+0x18c/0x190

Freed by task 357:
 kasan_save_stack+0x3c/0x70
 kasan_set_track+0x2c/0x40
 kasan_save_free_info+0x38/0x5c
 ____kasan_slab_free+0x13c/0x1b0
 __kasan_slab_free+0x18/0x24
 __kmem_cache_free+0x130/0x2e0
 kfree+0x5c/0xac
 mbox_test_message_write+0x208/0x29c
 full_proxy_write+0x90/0xf0
 vfs_write+0x154/0x440
 ksys_write+0xcc/0x180
 __arm64_sys_write+0x44/0x60
 invoke_syscall+0x60/0x190
 el0_svc_common.constprop.0+0x7c/0x160
 do_el0_svc+0x40/0xf0
 el0_svc+0x2c/0x6c
 el0t_64_sync_handler+0xf4/0x120
 el0t_64_sync+0x18c/0x190

Signed-off-by: Lee Jones lee@kernel.org Signed-off-by: Jassi Brar jaswinder.singh@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org

---

drivers/mailbox/mailbox-test.c | 7 +++++++ 1 file changed, 7 insertions(+)

Could you ensure the follow-up patch is also applied to all branches please?

8fe72b76db79d mailbox: mailbox-test: fix a locking issue in mbox_test_message_write()