Todd Kjos d35d3660e0 binder: fix null deref of proc->context ... The binder driver makes the assumption proc->context pointer is invariant after initialization (as documented in the kerneldoc header for struct proc). However, in commit f0fe2c0f05 ("binder: prevent UAF for binderfs devices II") proc->context is set to NULL during binder_deferred_release(). Another proc was in the middle of setting up a transaction to the dying process and crashed on a NULL pointer deref on "context" which is a local set to &proc->context: new_ref->data.desc = (node == context->binder_context_mgr_node) ? 0 : 1; Here's the stack: [ 5237.855435] Call trace: [ 5237.855441] binder_get_ref_for_node_olocked+0x100/0x2ec [ 5237.855446] binder_inc_ref_for_node+0x140/0x280 [ 5237.855451] binder_translate_binder+0x1d0/0x388 [ 5237.855456] binder_transaction+0x2228/0x3730 [ 5237.855461] binder_thread_write+0x640/0x25bc [ 5237.855466] binder_ioctl_write_read+0xb0/0x464 [ 5237.855471] binder_ioctl+0x30c/0x96c [ 5237.855477] do_vfs_ioctl+0x3e0/0x700 [ 5237.855482] __arm64_sys_ioctl+0x78/0xa4 [ 5237.855488] el0_svc_common+0xb4/0x194 [ 5237.855493] el0_svc_handler+0x74/0x98 [ 5237.855497] el0_svc+0x8/0xc The fix is to move the kfree of the binder_device to binder_free_proc() so the binder_device is freed when we know there are no references remaining on the binder_proc. Fixes: f0fe2c0f05 ("binder: prevent UAF for binderfs devices II") Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Todd Kjos <tkjos@google.com> Cc: stable <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20200622200715.114382-1-tkjos@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-06-23 07:54:46 +02:00
..
binder_alloc_selftest.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282	2019-06-05 17:36:37 +02:00
binder_alloc.c	mmap locking API: convert mmap_sem API comments	2020-06-09 09:39:14 -07:00
binder_alloc.h	binder: return errors from buffer copy functions	2019-07-01 08:42:47 +02:00
binder_internal.h	binder: prevent UAF for binderfs devices II	2020-03-03 19:58:37 +01:00
binder_trace.h	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282	2019-06-05 17:36:37 +02:00
binder.c	binder: fix null deref of proc->context	2020-06-23 07:54:46 +02:00
binderfs.c	binderfs: remove redundant assignment to pointer ctx	2020-04-23 16:48:11 +02:00
Kconfig	treewide: replace '---help---' in Kconfig files with 'help'	2020-06-14 01:57:21 +09:00
Makefile	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00