[BUG] security/keys: out-of-bounds in tpm2_unseal_trusted()

[co]

We found a bug reachable in:

    path    security/keys/trusted-keys
    crash   out-of-bounds in tpm2_unseal_trusted()
    commit  2709dd5ae32f ("Merge tag 'sched-urgent-2026-08-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip")

Config, environment, the sanitizer report and a C reproducer follow.

== Notes ===============================================================
    If you patch the bug based on our artifacts, a tag would be
    appreciated:

Reported-by: co+6a581c4284f721d4@xxxxxxx

    Everything in this mail is validated by the reproducer below.

    We also hold an LLM-generated root-cause analysis and a candidate
    patch. The patch passes an A/B test: the same reproducer panics the
    unpatched kernel and runs clean on the patched one. Neither has had
    human review, so both still require validation before you send or
    apply them. Available on:

        patch.diff  https://bugs.sh/b/6a581c4284f721d4/patch.diff
        report.md   https://bugs.sh/b/6a581c4284f721d4/report.md

    This is an open science project. The code and the full set of PoCs
    are not public at this moment, as we intend to disclose our findings
    in an ethical way.

    Happy to test patches. Complaints and suggestions about our work
    are welcome at:

        cedalion@xxxxxxx

== Environment =========================================================
    Reproduced on  2709dd5ae32f ("Merge tag 'sched-urgent-2026-08-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip")
    VM setup       https://bugs.sh/b/6a581c4284f721d4/run.sh
    config         https://bugs.sh/b/6a581c4284f721d4/config.gz
    poc            https://bugs.sh/b/6a581c4284f721d4/repro.c

== Sanitizer Report ====================================================
BUG: KASAN: slab-out-of-bounds in tpm2_unseal_trusted (./include/linux/unaligned.h:48 (discriminator 1) security/keys/trusted-keys/trusted_tpm2.c:408 (discriminator 1) security/keys/trusted-keys/trusted_tpm2.c:595 (discriminator 1))
Read of size 2 at addr ffff8880125db7aa by task exploit/149
CPU: 0 UID: 1000 PID: 149 Comm: exploit Tainted: G        W           7.2.0+ #31 PREEMPTLAZY
Call Trace:
dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
print_report (mm/kasan/report.c:378 mm/kasan/report.c:482)
kasan_report (mm/kasan/report.c:595)
tpm2_unseal_trusted (./include/linux/unaligned.h:48 (discriminator 1) security/keys/trusted-keys/trusted_tpm2.c:408 (discriminator 1) security/keys/trusted-keys/trusted_tpm2.c:595 (discriminator 1))
trusted_tpm_unseal (security/keys/trusted-keys/trusted_tpm1.c:928)
trusted_instantiate (security/keys/trusted-keys/trusted_core.c:196)
__key_instantiate_and_link (security/keys/key.c:446)
__key_create_or_update (security/keys/key.c:941)
key_create_or_update (security/keys/key.c:1021)
__do_sys_add_key (security/keys/keyctl.c:134)
do_syscall_64 (arch/x86/entry/syscall_64.c:61 arch/x86/entry/syscall_64.c:84)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
Allocated by task 149:
kasan_save_stack (mm/kasan/common.c:57)
kasan_save_track (mm/kasan/common.c:78)
__kasan_kmalloc (mm/kasan/common.c:398 mm/kasan/common.c:415)
__kmalloc_noprof (./include/linux/kasan.h:263 mm/slub.c:5337 mm/slub.c:5362)
tpm2_unseal_trusted (./include/linux/slab.h:992 security/keys/trusted-keys/trusted_tpm2.c:119 security/keys/trusted-keys/trusted_tpm2.c:384 security/keys/trusted-keys/trusted_tpm2.c:595)
trusted_tpm_unseal (security/keys/trusted-keys/trusted_tpm1.c:928)
trusted_instantiate (security/keys/trusted-keys/trusted_core.c:196)
__key_instantiate_and_link (security/keys/key.c:446)
__key_create_or_update (security/keys/key.c:941)
key_create_or_update (security/keys/key.c:1021)
__do_sys_add_key (security/keys/keyctl.c:134)
do_syscall_64 (arch/x86/entry/syscall_64.c:61 arch/x86/entry/syscall_64.c:84)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
The buggy address belongs to the object at ffff8880125db7a0
which belongs to the cache kmalloc-8 of size 8
The buggy address is located 2 bytes to the right of
allocated 8-byte region [ffff8880125db7a0, ffff8880125db7a8)
The buggy address belongs to the physical page:
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8880125db680: 00 fc fc fc fa fc fc fc 00 fc fc fc fc fc fc fc
ffff8880125db700: fc fc fc fc fc fc fc fc fa fc fc fc 00 fc fc fc
>ffff8880125db780: fc fc fc fc 00 fc fc fc fa fc fc fc fc fc fc fc
^
ffff8880125db800: fc fc fc fc fa fc fc fc 07 fc fc fc fc fc fc fc
ffff8880125db880: fa fc fc fc fc fc fc fc fc fc fc fc 00 fc fc fc


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