CVE-2026-64320
nvmet: fix pre-auth out-of-bounds heap read in Discovery Get Log Page
In the Linux kernel, the following vulnerability has been resolved:
nvmet: fix pre-auth out-of-bounds heap read in Discovery Get Log Page
nvmet_execute_disc_get_log_page() validates only the dword alignment
of the host-supplied Log Page Offset (lpo). The 64-bit offset is then
added to a small kzalloc'd buffer that holds the discovery log page
and the result is passed straight to nvmet_copy_to_sgl(), which
memcpy()s data_len bytes out to the host with no source-side bound
check:
u64 offset = nvmet_get_log_page_offset(req->cmd); /* 64-bit host */
size_t data_len = nvmet_get_log_page_len(req->cmd); /* 32-bit host */
...
if (offset & 0x3) { ... } /* only check */
...
alloc_len = sizeof(*hdr) + entry_size * discovery_log_entries(req);
buffer = kzalloc(alloc_len, GFP_KERNEL);
...
status = nvmet_copy_to_sgl(req, 0, buffer + offset, data_len);
The Discovery controller is unauthenticated -- nvmet_host_allowed()
returns true unconditionally for the discovery subsystem -- so the call
is reachable pre-authentication by any TCP/RDMA/FC peer that can reach
the nvmet target. With a discovery log page of ~1 KiB, an attacker
requesting up to 4 KiB starting at offset == alloc_len reads the next
slab page out and gets its content returned over the fabric (an
empirical run on a default nvmet-tcp loopback target leaked 81
canonical kernel pointers in one Get Log Page response). Pointing the
offset at unmapped kernel memory faults the in-kernel memcpy and
crashes (or panics, on panic_on_oops=1) the target host instead.
The attacker-controlled source-side offset pattern
"nvmet_copy_to_sgl(req, 0, buffer + ATTACKER_OFFSET, ...)" is unique
to nvmet_execute_disc_get_log_page in the entire nvmet codebase: every
other Get Log Page handler in admin-cmd.c either ignores lpo (and
silently starts every response at offset 0) or tracks a local
destination offset with a fixed source pointer.
Validate the host-supplied offset against the log page size, cap the
copy length to what is actually available, and zero-fill any remainder
of the host transfer buffer. The zero-fill matches the existing
short-response pattern in nvmet_execute_get_log_changed_ns()
(admin-cmd.c) and prevents leaking transport SGL contents when the
host asks for more bytes than the log page contains.
