FAILED: patch "[PATCH] KEYS: trusted: Fix TPM teardown ordering" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 5e2d672280d97d83de43031d93761b12dadd7b8a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090320-bagful-script-16a2@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5e2d672280d97d83de43031d93761b12dadd7b8a Mon Sep 17 00:00:00 2001
From: Chengfeng Ye <[email protected]>
Date: Tue, 11 Aug 2026 02:56:03 +0300
Subject: [PATCH] KEYS: trusted: Fix TPM teardown ordering

trusted_tpm_exit() drops the TPM chip reference and frees the digest array before unregistering the trusted key type. key_type_lookup() holds key_types_sem for reading until the key operation finishes, while unregister_key_type() takes it for writing. It therefore provides the synchronization point that must precede backend teardown.

The current order permits this interleaving:

CPU 0 CPU 1
trusted_tpm_exit() key_type_lookup("trusted")
put_device(&chip->dev) trusted_tpm_seal()
kfree(digests) pcrlock()
unregister_key_type() tpm_pcr_extend(..., digests)

CPU 1 can consequently dereference the freed digest array. The chip can also be released before callbacks stop using it.

KASAN reported:

  BUG: KASAN: slab-use-after-free in tpm_pcr_extend+0x1f0/0x200
  Read of size 2 at addr ffff88810872d000 by task poc/89
  Call Trace:
    tpm_pcr_extend+0x1f0/0x200
    pcrlock+0x42/0x70 [trusted]
    trusted_tpm_seal+0x1b6/0x570 [trusted]
    trusted_instantiate+0x293/0x340 [trusted]
    __key_instantiate_and_link+0xb2/0x2b0
    __key_create_or_update+0x61e/0xb50
    __do_sys_add_key+0x1b8/0x310
  Allocated by task 88:
    __kmalloc_noprof+0x1a7/0x490
    do_one_initcall+0xa1/0x390
    do_init_module+0x2df/0x840
  Freed by task 90:
    kfree+0x131/0x3c0
    trusted_tpm_exit+0x59/0xa0 [trusted]
    __do_sys_delete_module+0x346/0x510

Move unregister_key_type() before releasing either resource. This stops new lookups and waits for in-flight key operations to finish before the backend state is destroyed.

index 13513819991e..8f57c6111e7e 100644
@@ -987,9 +987,9 @@ static int __init trusted_tpm_init(void)
 static void trusted_tpm_exit(void)
 {
 	if (chip) {
+		unregister_key_type(&key_type_trusted);
 		put_device(&chip->dev);
 		kfree(digests);
-		unregister_key_type(&key_type_trusted);
 	}
 }
 

From: Chengfeng Ye <[email protected]>

[ Upstream commit 5e2d672280d97d83de43031d93761b12dadd7b8a ]

trusted_tpm_exit() drops the TPM chip reference and frees the digest array before unregistering the trusted key type. key_type_lookup() holds key_types_sem for reading until the key operation finishes, while unregister_key_type() takes it for writing. It therefore provides the synchronization point that must precede backend teardown.

The current order permits this interleaving:

CPU 0 CPU 1
trusted_tpm_exit() key_type_lookup("trusted")
put_device(&chip->dev) trusted_tpm_seal()
kfree(digests) pcrlock()
unregister_key_type() tpm_pcr_extend(..., digests)

CPU 1 can consequently dereference the freed digest array. The chip can also be released before callbacks stop using it.

KASAN reported:

  BUG: KASAN: slab-use-after-free in tpm_pcr_extend+0x1f0/0x200
  Read of size 2 at addr ffff88810872d000 by task poc/89
  Call Trace:
    tpm_pcr_extend+0x1f0/0x200
    pcrlock+0x42/0x70 [trusted]
    trusted_tpm_seal+0x1b6/0x570 [trusted]
    trusted_instantiate+0x293/0x340 [trusted]
    __key_instantiate_and_link+0xb2/0x2b0
    __key_create_or_update+0x61e/0xb50
    __do_sys_add_key+0x1b8/0x310
  Allocated by task 88:
    __kmalloc_noprof+0x1a7/0x490
    do_one_initcall+0xa1/0x390
    do_init_module+0x2df/0x840
  Freed by task 90:
    kfree+0x131/0x3c0
    trusted_tpm_exit+0x59/0xa0 [trusted]
    __do_sys_delete_module+0x346/0x510

Move unregister_key_type() before releasing either resource. This stops new lookups and waits for in-flight key operations to finish before the backend state is destroyed.

---
 security/keys/trusted-keys/trusted_tpm1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index ddcbfaede6849..3b1ee879419c4 100644
@@ -1058,10 +1058,10 @@ static int __init trusted_tpm_init(void)
 static void trusted_tpm_exit(void)
 {
 	if (chip) {
+		unregister_key_type(&key_type_trusted);
 		put_device(&chip->dev);
 		kfree(digests);
 		trusted_shash_release();
-		unregister_key_type(&key_type_trusted);
 	}
 }
 

2.53.0