tee: fix NULL pointer dereference in tee_shm_put

tee_shm_put have NULL pointer dereference:

__optee_disable_shm_cache -->
	shm = reg_pair_to_ptr(...);//shm maybe return NULL
        tee_shm_free(shm); -->
		tee_shm_put(shm);//crash

Add check in tee_shm_put to fix it.

panic log:
Unable to handle kernel paging request at virtual address 0000000000100cca
Mem abort info:
ESR = 0x0000000096000004
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x04: level 0 translation fault
Data abort info:
ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
CM = 0, WnR = 0, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=0000002049d07000
[0000000000100cca] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 0000000096000004 [#1] SMP
CPU: 2 PID: 14442 Comm: systemd-sleep Tainted: P OE ------- ----
6.6.0-39-generic torvalds#38
Source Version: 938b255f6cb8817c95b0dd5c8c2944acfce94b07
Hardware name: greatwall GW-001Y1A-FTH, BIOS Great Wall BIOS V3.0
10/26/2022
pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : tee_shm_put+0x24/0x188
lr : tee_shm_free+0x14/0x28
sp : ffff001f98f9faf0
x29: ffff001f98f9faf0 x28: ffff0020df543cc0 x27: 0000000000000000
x26: ffff001f811344a0 x25: ffff8000818dac00 x24: ffff800082d8d048
x23: ffff001f850fcd18 x22: 0000000000000001 x21: ffff001f98f9fb88
x20: ffff001f83e76218 x19: ffff001f83e761e0 x18: 000000000000ffff
x17: 303a30303a303030 x16: 0000000000000000 x15: 0000000000000003
x14: 0000000000000001 x13: 0000000000000000 x12: 0101010101010101
x11: 0000000000000001 x10: 0000000000000001 x9 : ffff800080e08d0c
x8 : ffff001f98f9fb88 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
x2 : ffff001f83e761e0 x1 : 00000000ffff001f x0 : 0000000000100cca
Call trace:
tee_shm_put+0x24/0x188
tee_shm_free+0x14/0x28
__optee_disable_shm_cache+0xa8/0x108
optee_shutdown+0x28/0x38
platform_shutdown+0x28/0x40
device_shutdown+0x144/0x2b0
kernel_power_off+0x3c/0x80
hibernate+0x35c/0x388
state_store+0x64/0x80
kobj_attr_store+0x14/0x28
sysfs_kf_write+0x48/0x60
kernfs_fop_write_iter+0x128/0x1c0
vfs_write+0x270/0x370
ksys_write+0x6c/0x100
__arm64_sys_write+0x20/0x30
invoke_syscall+0x4c/0x120
el0_svc_common.constprop.0+0x44/0xf0
do_el0_svc+0x24/0x38
el0_svc+0x24/0x88
el0t_64_sync_handler+0x134/0x150
el0t_64_sync+0x14c/0x15

Fixes: dfd0743 ("tee: handle lookup of shm with reference count 0")
Signed-off-by: Pei Xiao <[email protected]>
Reviewed-by: Sumit Garg <[email protected]>
Signed-off-by: Jens Wiklander <[email protected]>

Author: Pei Xiao

drivers/tee/tee_shm.c

@@ -560,9 +560,13 @@ EXPORT_SYMBOL_GPL(tee_shm_get_from_id);
  */
 void tee_shm_put(struct tee_shm *shm)
 {
-	struct tee_device *teedev = shm->ctx->teedev;
+	struct tee_device *teedev;
 	bool do_release = false;
 
+	if (!shm || !shm->ctx || !shm->ctx->teedev)
+		return;
+
+	teedev = shm->ctx->teedev;
 	mutex_lock(&teedev->mutex);
 	if (refcount_dec_and_test(&shm->refcount)) {
 		/*