Re: [6.4-rc6] Crash during a kexec operation (tpm_amd_is_rng_defective)

[Michael Ellerman]

Sachin Sant <sachinp@xxxxxxxxxxxxx> writes:
> Following crash is observed during a kexec operation on 
> IBM Power10 server:
>
> [ 34.381548] Kernel attempted to read user page (50) - exploit attempt? (uid: 0)
> [ 34.381562] BUG: Kernel NULL pointer dereference on read at 0x00000050
> [ 34.381565] Faulting instruction address: 0xc0000000009db1e4
> [ 34.381569] Oops: Kernel access of bad area, sig: 11 [#1]
> [ 34.381572] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
> [ 34.381576] Modules linked in: dm_mod(E) nft_fib_inet(E) nft_fib_ipv4(E) nft_fib_ipv6(E) nft_fib(E) nft_reject_inet(E) nf_reject_ipv4(E) nf_reject_ipv6(E) nft_reject(E) nft_ct(E) nft_chain_nat(E) nf_nat(E) nf_conntrack(E) nf_defrag_ipv6(E) nf_defrag_ipv4(E) bonding(E) tls(E) rfkill(E) ip_set(E) sunrpc(E) nf_tables(E) nfnetlink(E) pseries_rng(E) aes_gcm_p10_crypto(E) drm(E) drm_panel_orientation_quirks(E) xfs(E) libcrc32c(E) sd_mod(E) sr_mod(E) t10_pi(E) crc64_rocksoft_generic(E) cdrom(E) crc64_rocksoft(E) crc64(E) sg(E) ibmvscsi(E) scsi_transport_srp(E) ibmveth(E) vmx_crypto(E) fuse(E)
> [ 34.381613] CPU: 18 PID: 5918 Comm: kexec Kdump: loaded Tainted: G E 6.4.0-rc6-00037-gb6dad5178cea #3
> [ 34.381618] Hardware name: IBM,9080-HEX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1030.20 (NH1030_058) hv:phyp pSeries
> [ 34.381621] NIP: c0000000009db1e4 LR: c0000000009db928 CTR: c0000000009eab60
> [ 34.381625] REGS: c00000009742f780 TRAP: 0300 Tainted: G E (6.4.0-rc6-00037-gb6dad5178cea)
> [ 34.381628] MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 44488884 XER: 00000001
> [ 34.381638] CFAR: c0000000009db19c DAR: 0000000000000050 DSISR: 40000000 IRQMASK: 0 
> [ 34.381638] GPR00: c0000000009db928 c00000009742fa20 c0000000014a1500 c0000000081d0000 
> [ 34.381638] GPR04: c00000000d842c50 c00000000d842c50 0000000000000025 fffffffffffe0000 
> [ 34.381638] GPR08: 0000000000000000 0000000000000000 0000000000000009 c008000000785280 
> [ 34.381638] GPR12: c0000000009eab60 c00000135fab7f00 0000000000000000 0000000000000000 
> [ 34.381638] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
> [ 34.381638] GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
> [ 34.381638] GPR24: 0000000000000000 0000000000000000 0000000000000000 c000000002e21e08 
> [ 34.381638] GPR28: c00000000d842c48 c000000002a02208 c00000000321c0c0 c0000000081d0000 
> [ 34.381674] NIP [c0000000009db1e4] tpm_amd_is_rng_defective+0x74/0x240
> [ 34.381681] LR [c0000000009db928] tpm_chip_unregister+0x138/0x160
> [ 34.381685] Call Trace:
> [ 34.381686] [c00000009742faa0] [c0000000009db928] tpm_chip_unregister+0x138/0x160
> [ 34.381690] [c00000009742fae0] [c0000000009eab94] tpm_ibmvtpm_remove+0x34/0x130
...
> [ 34.381788] Code: 5463063e 408201c8 38210080 4e800020 60000000 60000000 60000000 7c0802a6 fbe10078 7c7f1b78 f8010090 e9230728 <e9890050> 2c2c0000 41820020 7d8903a6 

  2c:   28 07 23 e9     ld      r9,1832(r3)
  30:   50 00 89 e9     ld      r12,80(r9)

Where r3 is *chip.
r9 is NULL, and 80 = 0x50.

Looks like a NULL chip->ops, which oopses in:

static int tpm_request_locality(struct tpm_chip *chip)
{
	int rc;

	if (!chip->ops->request_locality)


Can you test the patch below?

cheers


diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index cd48033b804a..82eb36e2e16d 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -36,7 +36,7 @@ static int tpm_request_locality(struct tpm_chip *chip)
 {
 	int rc;
 
-	if (!chip->ops->request_locality)
+	if (!chip->ops || !chip->ops->request_locality)
 		return 0;
 
 	rc = chip->ops->request_locality(chip, 0);