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When ne_create_vm_ioctl() fails the SLOT_ALLOC request after
anon_inode_getfile() has succeeded, the error path calls
fput(enclave_file) and then frees ne_enclave.
In normal userspace context, fput() defers the final __fput() via
task_work. ne_enclave_release() therefore runs after ne_enclave has
already been freed and dereferences ne_enclave->slot_uid, causing a
use-after-free: KASAN: slab-use-after-free in ne_enclave_release.
The enclave has no slot allocated and is not yet linked into the
enclaves list on this error path, so ne_enclave_release() is expected
to return early when slot_uid is zero. However, reading slot_uid
already accesses the freed object.
Clear enclave_file->private_data before fput() on the error path.
ne_enclave_release() then returns immediately when private_data is
NULL, leaving the ioctl error path as the sole owner of ne_enclave.
This is safe because the file has not been fd_install()'d yet.
Tested on an AWS EC2 m5.2xlarge with CONFIG_KASAN=y. Without the
patch, the reproducer triggers a KASAN slab-use-after-free on every
SLOT_ALLOC failure. With the patch, no KASAN report is produced and
the SLOT_ALLOC error is still returned. Normal enclave creation and
teardown are unaffected.
Fixes: 9c8eb50fe9e2 ("nitro_enclaves: Add logic for terminating an enclave")
Cc: stable@vger.kernel.org
Co-developed-by: Zhaofeng Chen <zhaofeng.chen@certik.com>
Signed-off-by: Zhaofeng Chen <zhaofeng.chen@certik.com>
Signed-off-by: Yuxiao Wang <yuxiao.wang@certik.com>
Reviewed-by: Alexander Graf <graf@amazon.com>
Link: https://patch.msgid.link/20260909124400.27857-1-graf@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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