From: Bryam Vargas <hexlabsecurity@proton.me> mainline inclusion from mainline-v7.2-rc1 commit 53cd102a7a56079b11b897835bd9b94c14e6322c category: bugfix bugzilla: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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. Fixes: a07b4970f464 ("nvmet: add a generic NVMe target") Cc: stable@vger.kernel.org Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me> Signed-off-by: Keith Busch <kbusch@kernel.org> Conflicts: drivers/nvme/target/discovery.c [drivers/nvme/target/discovery.c: Replaced NVME_STATUS_DNR with NVME_SC_DNR; added copy_len variable and offset validation; used nvmet_zero_sgl for zero-fill remainder.] Signed-off-by: Lu Chentao <luchentao1@huawei.com> --- drivers/nvme/target/discovery.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/drivers/nvme/target/discovery.c b/drivers/nvme/target/discovery.c index 668d257fa986..d5f0abbbe406 100644 --- a/drivers/nvme/target/discovery.c +++ b/drivers/nvme/target/discovery.c @@ -164,10 +164,11 @@ static void nvmet_execute_disc_get_log_page(struct nvmet_req *req) struct nvmet_ctrl *ctrl = req->sq->ctrl; struct nvmf_disc_rsp_page_hdr *hdr; u64 offset = nvmet_get_log_page_offset(req->cmd); size_t data_len = nvmet_get_log_page_len(req->cmd); size_t alloc_len; + size_t copy_len; struct nvmet_subsys_link *p; struct nvmet_port *r; u32 numrec = 0; u16 status = 0; void *buffer; @@ -237,11 +238,31 @@ static void nvmet_execute_disc_get_log_page(struct nvmet_req *req) nvmet_clear_aen_bit(req, NVME_AEN_BIT_DISC_CHANGE); up_read(&nvmet_config_sem); - status = nvmet_copy_to_sgl(req, 0, buffer + offset, data_len); + /* + * Validate the host-supplied log page offset before copying out. + * Without this check, the host controls a 64-bit byte offset into + * a small kzalloc'd buffer: a value past the log page lets the + * subsequent memcpy read adjacent kernel heap, and a value aimed + * at unmapped kernel memory faults the in-kernel copy and crashes + * the target host. The Discovery controller is unauthenticated, + * so the bug is reachable from any reachable fabric peer. + */ + if (offset > alloc_len) { + req->error_loc = + offsetof(struct nvme_get_log_page_command, lpo); + status = NVME_SC_INVALID_FIELD | NVME_SC_DNR; + goto out_free_buffer; + } + + copy_len = min_t(size_t, data_len, alloc_len - offset); + status = nvmet_copy_to_sgl(req, 0, buffer + offset, copy_len); + if (!status && copy_len < data_len) + status = nvmet_zero_sgl(req, copy_len, data_len - copy_len); +out_free_buffer: kfree(buffer); out: nvmet_req_complete(req, status); } -- 2.52.0