From: Herbert Xu <herbert@gondor.apana.org.au>
To: Sean Christopherson <seanjc@google.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
John Allen <john.allen@amd.com>,
"David S. Miller" <davem@davemloft.net>,
linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] crypto: ccp: Treat zero-length cert chain as query for blob lengths
Date: Fri, 15 May 2026 18:14:34 +0800 [thread overview]
Message-ID: <agbyCoTIGkx5Lvlc@gondor.apana.org.au> (raw)
In-Reply-To: <20260504222812.2339526-1-seanjc@google.com>
On Mon, May 04, 2026 at 03:28:12PM -0700, Sean Christopherson wrote:
> When handling a PDH export, treat a zero-length userspace cert chain buffer
> as a request to query the length of the relevant blobs. Failure to account
> for the zero-length buffer trips a BUG_ON() when running with
> CONFIG_DEBUG_VIRTUAL=y due to trying to get the physical address of the
> ZERO_SIZE_PTR (returned by kzalloc() on the bogus allocation).
>
> kernel BUG at arch/x86/mm/physaddr.c:28 !
> Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
> CPU: 30 UID: 0 PID: 28580 Comm: syz.2.18 Kdump: loaded
> Tainted: G W 6.18.16-smp-DEV #1 NONE
> Tainted: [W]=WARN
> Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 12.62.0-0 11/19/2025
> RIP: 0010:__phys_addr+0x16a/0x180 arch/x86/mm/physaddr.c:28
> RSP: 0018:ffffc9008329fc80 EFLAGS: 00010293
> RAX: ffffffff8179110a RBX: 0000778000000010 RCX: ffff8884e6992600
> RDX: 0000000000000000 RSI: 0000000080000010 RDI: 0000778000000010
> RBP: ffffc9008329fdf0 R08: 0000000000000dc0 R09: 00000000ffffffff
> R10: dffffc0000000000 R11: fffffbfff126d297 R12: dffffc0000000000
> R13: 1ffff92010653fc8 R14: 0000000080000010 R15: dffffc0000000000
> FS: 0000555556bec9c0(0000) GS:ffff88aa4ce1c000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fd3159e7000 CR3: 00000004fbc44000 CR4: 0000000000350ef0
> Call Trace:
> <TASK>
> [<ffffffff853d3869>] sev_ioctl_do_pdh_export+0x559/0x7a0 drivers/crypto/ccp/sev-dev.c:2308
> [<ffffffff853d1fdd>] sev_ioctl+0x2cd/0x480 drivers/crypto/ccp/sev-dev.c:2556
> [<ffffffff82549ebc>] vfs_ioctl fs/ioctl.c:52 [inline]
> [<ffffffff82549ebc>] __do_sys_ioctl fs/ioctl.c:598 [inline]
> [<ffffffff82549ebc>] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
> [<ffffffff8630115f>] do_syscall_x64 arch/x86/entry/syscall_64.c:64 [inline]
> [<ffffffff8630115f>] do_syscall_64+0x9f/0xf40 arch/x86/entry/syscall_64.c:98
> [<ffffffff81000136>] entry_SYSCALL_64_after_hwframe+0x76/0x7e
> RIP: 0033:0x7fd3158eac39
> </TASK>
>
> Thankfully, the bug is benign outside of CONFIG_DEBUG_VIRTUAL=y as getting
> the physical address is just arithmetic, and the PSP errors out before
> trying to write to the garbage address (which it must, otherwise querying
> the blob lengths would clobber memory at pfn=0).
>
> Fixes: 76a2b524a4b1 ("crypto: ccp: Implement SEV_PDH_CERT_EXPORT ioctl command")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> drivers/crypto/ccp/sev-dev.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
Patch applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
prev parent reply other threads:[~2026-05-15 10:14 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-04 22:28 [PATCH] crypto: ccp: Treat zero-length cert chain as query for blob lengths Sean Christopherson
2026-05-05 14:32 ` Tom Lendacky
2026-05-15 10:14 ` Herbert Xu [this message]
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