From c5e81e672699e0c5557b2b755cc8f7a69aa92bff Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Mon, 25 Aug 2025 18:07:10 +0200 Subject: [PATCH 1/5] efi: stmm: Fix incorrect buffer allocation method The communication buffer allocated by setup_mm_hdr() is later on passed to tee_shm_register_kernel_buf(). The latter expects those buffers to be contiguous pages, but setup_mm_hdr() just uses kmalloc(). That can cause various corruptions or BUGs, specifically since commit 9aec2fb0fd5e ("slab: allocate frozen pages"), though it was broken before as well. Fix this by using alloc_pages_exact() instead of kmalloc(). Fixes: c44b6be62e8d ("efi: Add tee-based EFI variable driver") Signed-off-by: Jan Kiszka Acked-by: Ilias Apalodimas Acked-by: Sumit Garg Signed-off-by: Ard Biesheuvel --- drivers/firmware/efi/stmm/tee_stmm_efi.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/drivers/firmware/efi/stmm/tee_stmm_efi.c b/drivers/firmware/efi/stmm/tee_stmm_efi.c index f741ca279052..e15d11ed165e 100644 --- a/drivers/firmware/efi/stmm/tee_stmm_efi.c +++ b/drivers/firmware/efi/stmm/tee_stmm_efi.c @@ -143,6 +143,10 @@ static efi_status_t mm_communicate(u8 *comm_buf, size_t payload_size) return var_hdr->ret_status; } +#define COMM_BUF_SIZE(__payload_size) (MM_COMMUNICATE_HEADER_SIZE + \ + MM_VARIABLE_COMMUNICATE_SIZE + \ + (__payload_size)) + /** * setup_mm_hdr() - Allocate a buffer for StandAloneMM and initialize the * header data. @@ -173,9 +177,8 @@ static void *setup_mm_hdr(u8 **dptr, size_t payload_size, size_t func, return NULL; } - comm_buf = kzalloc(MM_COMMUNICATE_HEADER_SIZE + - MM_VARIABLE_COMMUNICATE_SIZE + payload_size, - GFP_KERNEL); + comm_buf = alloc_pages_exact(COMM_BUF_SIZE(payload_size), + GFP_KERNEL | __GFP_ZERO); if (!comm_buf) { *ret = EFI_OUT_OF_RESOURCES; return NULL; @@ -239,7 +242,7 @@ static efi_status_t get_max_payload(size_t *size) */ *size -= 2; out: - kfree(comm_buf); + free_pages_exact(comm_buf, COMM_BUF_SIZE(payload_size)); return ret; } @@ -282,7 +285,7 @@ static efi_status_t get_property_int(u16 *name, size_t name_size, memcpy(var_property, &smm_property->property, sizeof(*var_property)); out: - kfree(comm_buf); + free_pages_exact(comm_buf, COMM_BUF_SIZE(payload_size)); return ret; } @@ -347,7 +350,7 @@ static efi_status_t tee_get_variable(u16 *name, efi_guid_t *vendor, memcpy(data, (u8 *)var_acc->name + var_acc->name_size, var_acc->data_size); out: - kfree(comm_buf); + free_pages_exact(comm_buf, COMM_BUF_SIZE(payload_size)); return ret; } @@ -404,7 +407,7 @@ static efi_status_t tee_get_next_variable(unsigned long *name_size, memcpy(name, var_getnext->name, var_getnext->name_size); out: - kfree(comm_buf); + free_pages_exact(comm_buf, COMM_BUF_SIZE(payload_size)); return ret; } @@ -467,7 +470,7 @@ static efi_status_t tee_set_variable(efi_char16_t *name, efi_guid_t *vendor, ret = mm_communicate(comm_buf, payload_size); dev_dbg(pvt_data.dev, "Set Variable %s %d %lx\n", __FILE__, __LINE__, ret); out: - kfree(comm_buf); + free_pages_exact(comm_buf, COMM_BUF_SIZE(payload_size)); return ret; } @@ -507,7 +510,7 @@ static efi_status_t tee_query_variable_info(u32 attributes, *max_variable_size = mm_query_info->max_variable_size; out: - kfree(comm_buf); + free_pages_exact(comm_buf, COMM_BUF_SIZE(payload_size)); return ret; } From 80c6c1048625712200ab9cdc665d792b85594e2c Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Mon, 25 Aug 2025 18:07:11 +0200 Subject: [PATCH 2/5] efi: stmm: Do not return EFI_OUT_OF_RESOURCES on internal errors When we are low on memory or when the internal API is violated, we cannot return EFI_OUT_OF_RESOURCES. According to the UEFI standard, that error code is either related to persistent storage used for the variable or even not foreseen as possible error (GetVariable e.g.). Use the not fully accurate but compliant error code EFI_DEVICE_ERROR in those cases. Signed-off-by: Jan Kiszka Reviewed-by: Ilias Apalodimas Acked-by: Sumit Garg Signed-off-by: Ard Biesheuvel --- drivers/firmware/efi/stmm/tee_stmm_efi.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/firmware/efi/stmm/tee_stmm_efi.c b/drivers/firmware/efi/stmm/tee_stmm_efi.c index e15d11ed165e..8501056ade8a 100644 --- a/drivers/firmware/efi/stmm/tee_stmm_efi.c +++ b/drivers/firmware/efi/stmm/tee_stmm_efi.c @@ -218,7 +218,7 @@ static efi_status_t get_max_payload(size_t *size) SMM_VARIABLE_FUNCTION_GET_PAYLOAD_SIZE, &ret); if (!var_payload) - return EFI_OUT_OF_RESOURCES; + return EFI_DEVICE_ERROR; ret = mm_communicate(comm_buf, payload_size); if (ret != EFI_SUCCESS) @@ -264,7 +264,7 @@ static efi_status_t get_property_int(u16 *name, size_t name_size, &comm_buf, payload_size, SMM_VARIABLE_FUNCTION_VAR_CHECK_VARIABLE_PROPERTY_GET, &ret); if (!smm_property) - return EFI_OUT_OF_RESOURCES; + return EFI_DEVICE_ERROR; memcpy(&smm_property->guid, vendor, sizeof(smm_property->guid)); smm_property->name_size = name_size; @@ -320,7 +320,7 @@ static efi_status_t tee_get_variable(u16 *name, efi_guid_t *vendor, var_acc = setup_mm_hdr(&comm_buf, payload_size, SMM_VARIABLE_FUNCTION_GET_VARIABLE, &ret); if (!var_acc) - return EFI_OUT_OF_RESOURCES; + return EFI_DEVICE_ERROR; /* Fill in contents */ memcpy(&var_acc->guid, vendor, sizeof(var_acc->guid)); @@ -386,7 +386,7 @@ static efi_status_t tee_get_next_variable(unsigned long *name_size, SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME, &ret); if (!var_getnext) - return EFI_OUT_OF_RESOURCES; + return EFI_DEVICE_ERROR; /* Fill in contents */ memcpy(&var_getnext->guid, guid, sizeof(var_getnext->guid)); @@ -442,7 +442,7 @@ static efi_status_t tee_set_variable(efi_char16_t *name, efi_guid_t *vendor, var_acc = setup_mm_hdr(&comm_buf, payload_size, SMM_VARIABLE_FUNCTION_SET_VARIABLE, &ret); if (!var_acc) - return EFI_OUT_OF_RESOURCES; + return EFI_DEVICE_ERROR; /* * The API has the ability to override RO flags. If no RO check was @@ -498,7 +498,7 @@ static efi_status_t tee_query_variable_info(u32 attributes, SMM_VARIABLE_FUNCTION_QUERY_VARIABLE_INFO, &ret); if (!mm_query_info) - return EFI_OUT_OF_RESOURCES; + return EFI_DEVICE_ERROR; mm_query_info->attr = attributes; ret = mm_communicate(comm_buf, payload_size); From 01a3044af5d910e1f8b0bee53b2e0eccee8f9a5c Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Mon, 25 Aug 2025 18:07:12 +0200 Subject: [PATCH 3/5] efi: stmm: Drop unused EFI error from setup_mm_hdr arguments No caller ever evaluates what we return in 'ret'. They only use the return code of the function. Signed-off-by: Jan Kiszka Reviewed-by: Ilias Apalodimas Acked-by: Sumit Garg Signed-off-by: Ard Biesheuvel --- drivers/firmware/efi/stmm/tee_stmm_efi.c | 25 ++++++++---------------- 1 file changed, 8 insertions(+), 17 deletions(-) diff --git a/drivers/firmware/efi/stmm/tee_stmm_efi.c b/drivers/firmware/efi/stmm/tee_stmm_efi.c index 8501056ade8a..c2bc8467b099 100644 --- a/drivers/firmware/efi/stmm/tee_stmm_efi.c +++ b/drivers/firmware/efi/stmm/tee_stmm_efi.c @@ -154,11 +154,9 @@ static efi_status_t mm_communicate(u8 *comm_buf, size_t payload_size) * @dptr: pointer address to store allocated buffer * @payload_size: payload size * @func: standAloneMM function number - * @ret: EFI return code * Return: pointer to corresponding StandAloneMM function buffer or NULL */ -static void *setup_mm_hdr(u8 **dptr, size_t payload_size, size_t func, - efi_status_t *ret) +static void *setup_mm_hdr(u8 **dptr, size_t payload_size, size_t func) { const efi_guid_t mm_var_guid = EFI_MM_VARIABLE_GUID; struct efi_mm_communicate_header *mm_hdr; @@ -173,16 +171,13 @@ static void *setup_mm_hdr(u8 **dptr, size_t payload_size, size_t func, if (max_buffer_size && max_buffer_size < (MM_COMMUNICATE_HEADER_SIZE + MM_VARIABLE_COMMUNICATE_SIZE + payload_size)) { - *ret = EFI_INVALID_PARAMETER; return NULL; } comm_buf = alloc_pages_exact(COMM_BUF_SIZE(payload_size), GFP_KERNEL | __GFP_ZERO); - if (!comm_buf) { - *ret = EFI_OUT_OF_RESOURCES; + if (!comm_buf) return NULL; - } mm_hdr = (struct efi_mm_communicate_header *)comm_buf; memcpy(&mm_hdr->header_guid, &mm_var_guid, sizeof(mm_hdr->header_guid)); @@ -192,7 +187,6 @@ static void *setup_mm_hdr(u8 **dptr, size_t payload_size, size_t func, var_hdr->function = func; if (dptr) *dptr = comm_buf; - *ret = EFI_SUCCESS; return var_hdr->data; } @@ -215,8 +209,7 @@ static efi_status_t get_max_payload(size_t *size) payload_size = sizeof(*var_payload); var_payload = setup_mm_hdr(&comm_buf, payload_size, - SMM_VARIABLE_FUNCTION_GET_PAYLOAD_SIZE, - &ret); + SMM_VARIABLE_FUNCTION_GET_PAYLOAD_SIZE); if (!var_payload) return EFI_DEVICE_ERROR; @@ -262,7 +255,7 @@ static efi_status_t get_property_int(u16 *name, size_t name_size, smm_property = setup_mm_hdr( &comm_buf, payload_size, - SMM_VARIABLE_FUNCTION_VAR_CHECK_VARIABLE_PROPERTY_GET, &ret); + SMM_VARIABLE_FUNCTION_VAR_CHECK_VARIABLE_PROPERTY_GET); if (!smm_property) return EFI_DEVICE_ERROR; @@ -318,7 +311,7 @@ static efi_status_t tee_get_variable(u16 *name, efi_guid_t *vendor, payload_size = MM_VARIABLE_ACCESS_HEADER_SIZE + name_size + tmp_dsize; var_acc = setup_mm_hdr(&comm_buf, payload_size, - SMM_VARIABLE_FUNCTION_GET_VARIABLE, &ret); + SMM_VARIABLE_FUNCTION_GET_VARIABLE); if (!var_acc) return EFI_DEVICE_ERROR; @@ -383,8 +376,7 @@ static efi_status_t tee_get_next_variable(unsigned long *name_size, payload_size = MM_VARIABLE_GET_NEXT_HEADER_SIZE + out_name_size; var_getnext = setup_mm_hdr(&comm_buf, payload_size, - SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME, - &ret); + SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME); if (!var_getnext) return EFI_DEVICE_ERROR; @@ -440,7 +432,7 @@ static efi_status_t tee_set_variable(efi_char16_t *name, efi_guid_t *vendor, * the properties, if the allocation fails */ var_acc = setup_mm_hdr(&comm_buf, payload_size, - SMM_VARIABLE_FUNCTION_SET_VARIABLE, &ret); + SMM_VARIABLE_FUNCTION_SET_VARIABLE); if (!var_acc) return EFI_DEVICE_ERROR; @@ -495,8 +487,7 @@ static efi_status_t tee_query_variable_info(u32 attributes, payload_size = sizeof(*mm_query_info); mm_query_info = setup_mm_hdr(&comm_buf, payload_size, - SMM_VARIABLE_FUNCTION_QUERY_VARIABLE_INFO, - &ret); + SMM_VARIABLE_FUNCTION_QUERY_VARIABLE_INFO); if (!mm_query_info) return EFI_DEVICE_ERROR; From 134ed1093907a79e5d98087513f13fd7652c4df9 Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Mon, 25 Aug 2025 18:07:13 +0200 Subject: [PATCH 4/5] efi: stmm: Drop unneeded null pointer check The API documenation of setup_mm_hdr does not mention that dptr can be NULL, this is a local function, and no caller passes NULL. So drop the unneeded check. Signed-off-by: Jan Kiszka Reviewed-by: Ilias Apalodimas Acked-by: Sumit Garg Signed-off-by: Ard Biesheuvel --- drivers/firmware/efi/stmm/tee_stmm_efi.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/firmware/efi/stmm/tee_stmm_efi.c b/drivers/firmware/efi/stmm/tee_stmm_efi.c index c2bc8467b099..65c0fe1ba275 100644 --- a/drivers/firmware/efi/stmm/tee_stmm_efi.c +++ b/drivers/firmware/efi/stmm/tee_stmm_efi.c @@ -185,8 +185,7 @@ static void *setup_mm_hdr(u8 **dptr, size_t payload_size, size_t func) var_hdr = (struct smm_variable_communicate_header *)mm_hdr->data; var_hdr->function = func; - if (dptr) - *dptr = comm_buf; + *dptr = comm_buf; return var_hdr->data; } From a6358f8cf64850f3f27857b8ed8c1b08cfc4685c Mon Sep 17 00:00:00 2001 From: Li Nan Date: Wed, 27 Aug 2025 15:39:54 +0800 Subject: [PATCH 5/5] efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare Observed on kernel 6.6 (present on master as well): BUG: KASAN: slab-out-of-bounds in memcmp+0x98/0xd0 Call trace: kasan_check_range+0xe8/0x190 __asan_loadN+0x1c/0x28 memcmp+0x98/0xd0 efivarfs_d_compare+0x68/0xd8 __d_lookup_rcu_op_compare+0x178/0x218 __d_lookup_rcu+0x1f8/0x228 d_alloc_parallel+0x150/0x648 lookup_open.isra.0+0x5f0/0x8d0 open_last_lookups+0x264/0x828 path_openat+0x130/0x3f8 do_filp_open+0x114/0x248 do_sys_openat2+0x340/0x3c0 __arm64_sys_openat+0x120/0x1a0 If dentry->d_name.len < EFI_VARIABLE_GUID_LEN , 'guid' can become negative, leadings to oob. The issue can be triggered by parallel lookups using invalid filename: T1 T2 lookup_open ->lookup simple_lookup d_add // invalid dentry is added to hash list lookup_open d_alloc_parallel __d_lookup_rcu __d_lookup_rcu_op_compare hlist_bl_for_each_entry_rcu // invalid dentry can be retrieved ->d_compare efivarfs_d_compare // oob Fix it by checking 'guid' before cmp. Fixes: da27a24383b2 ("efivarfs: guid part of filenames are case-insensitive") Signed-off-by: Li Nan Signed-off-by: Wu Guanghao Signed-off-by: Ard Biesheuvel --- fs/efivarfs/super.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c index c4a139911356..4bb4002e3cdf 100644 --- a/fs/efivarfs/super.c +++ b/fs/efivarfs/super.c @@ -152,6 +152,10 @@ static int efivarfs_d_compare(const struct dentry *dentry, { int guid = len - EFI_VARIABLE_GUID_LEN; + /* Parallel lookups may produce a temporary invalid filename */ + if (guid <= 0) + return 1; + if (name->len != len) return 1;