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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: linux-efi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
	Arend van Spriel <arend.vanspriel@broadcom.com>,
	Bhupesh Sharma <bhsharma@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@intel.com>,
	Eric Snowberg <eric.snowberg@oracle.com>,
	Hans de Goede <hdegoede@redhat.com>,
	Joe Perches <joe@perches.com>, Jon Hunter <jonathanh@nvidia.com>,
	Julien Thierry <julien.thierry@arm.com>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
	Sedat Dilek <sedat.dilek@gmail.com>,
	YiFei Zhu <zhuyifei1999@gmail.com>
Subject: [PATCH 08/11] firmware: efi: add NULL pointer checks in efivars api functions
Date: Thu, 29 Nov 2018 18:12:27 +0100
Message-ID: <20181129171230.18699-9-ard.biesheuvel@linaro.org> (raw)
In-Reply-To: <20181129171230.18699-1-ard.biesheuvel@linaro.org>

From: Arend van Spriel <arend.vanspriel@broadcom.com>

Since commit:

   ce2e6db554fa ("brcmfmac: Add support for getting nvram contents from
                 EFI variables")

we have a device driver accessing the efivars API. Several functions in
the efivars API assume __efivars is set, i.e., that they will be accessed
only after efivars_register() has been called. However, the following NULL
pointer access was reported calling efivar_entry_size() from the brcmfmac
device driver.

  Unable to handle kernel NULL pointer dereference at virtual address 00000008
  pgd = 60bfa5f1
  [00000008] *pgd=00000000
  Internal error: Oops: 5 [#1] SMP ARM
  ...
  Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
  Workqueue: events request_firmware_work_func
  PC is at efivar_entry_size+0x28/0x90
  LR is at brcmf_fw_complete_request+0x3f8/0x8d4 [brcmfmac]
  pc : [<c0c40718>]    lr : [<bf2a3ef4>]    psr: a00d0113
  sp : ede7fe28  ip : ee983410  fp : c1787f30
  r10: 00000000  r9 : 00000000  r8 : bf2b2258
  r7 : ee983000  r6 : c1604c48  r5 : ede7fe88  r4 : edf337c0
  r3 : 00000000  r2 : 00000000  r1 : ede7fe88  r0 : c17712c8
  Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
  Control: 10c5387d  Table: ad16804a  DAC: 00000051

Disassembly showed that the local static variable __efivars is NULL,
which is not entirely unexpected given that it is a non-EFI platform.
So add a NULL pointer check to efivar_entry_size(), and to related
functions while at it. In efivars_register() a couple of sanity checks
are added as well.

Cc: Hans de Goede <hdegoede@redhat.com>
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/firmware/efi/vars.c | 99 +++++++++++++++++++++++++++++--------
 1 file changed, 78 insertions(+), 21 deletions(-)

diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 9336ffdf6e2c..fceaafd67ec6 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -318,7 +318,12 @@ EXPORT_SYMBOL_GPL(efivar_variable_is_removable);
 static efi_status_t
 check_var_size(u32 attributes, unsigned long size)
 {
-	const struct efivar_operations *fops = __efivars->ops;
+	const struct efivar_operations *fops;
+
+	if (!__efivars)
+		return EFI_UNSUPPORTED;
+
+	fops = __efivars->ops;
 
 	if (!fops->query_variable_store)
 		return EFI_UNSUPPORTED;
@@ -329,7 +334,12 @@ check_var_size(u32 attributes, unsigned long size)
 static efi_status_t
 check_var_size_nonblocking(u32 attributes, unsigned long size)
 {
-	const struct efivar_operations *fops = __efivars->ops;
+	const struct efivar_operations *fops;
+
+	if (!__efivars)
+		return EFI_UNSUPPORTED;
+
+	fops = __efivars->ops;
 
 	if (!fops->query_variable_store)
 		return EFI_UNSUPPORTED;
@@ -429,13 +439,18 @@ static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid,
 int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
 		void *data, bool duplicates, struct list_head *head)
 {
-	const struct efivar_operations *ops = __efivars->ops;
+	const struct efivar_operations *ops;
 	unsigned long variable_name_size = 1024;
 	efi_char16_t *variable_name;
 	efi_status_t status;
 	efi_guid_t vendor_guid;
 	int err = 0;
 
+	if (!__efivars)
+		return -EFAULT;
+
+	ops = __efivars->ops;
+
 	variable_name = kzalloc(variable_name_size, GFP_KERNEL);
 	if (!variable_name) {
 		printk(KERN_ERR "efivars: Memory allocation failed.\n");
@@ -583,12 +598,14 @@ static void efivar_entry_list_del_unlock(struct efivar_entry *entry)
  */
 int __efivar_entry_delete(struct efivar_entry *entry)
 {
-	const struct efivar_operations *ops = __efivars->ops;
 	efi_status_t status;
 
-	status = ops->set_variable(entry->var.VariableName,
-				   &entry->var.VendorGuid,
-				   0, 0, NULL);
+	if (!__efivars)
+		return -EINVAL;
+
+	status = __efivars->ops->set_variable(entry->var.VariableName,
+					      &entry->var.VendorGuid,
+					      0, 0, NULL);
 
 	return efi_status_to_err(status);
 }
@@ -607,12 +624,17 @@ EXPORT_SYMBOL_GPL(__efivar_entry_delete);
  */
 int efivar_entry_delete(struct efivar_entry *entry)
 {
-	const struct efivar_operations *ops = __efivars->ops;
+	const struct efivar_operations *ops;
 	efi_status_t status;
 
 	if (down_interruptible(&efivars_lock))
 		return -EINTR;
 
+	if (!__efivars) {
+		up(&efivars_lock);
+		return -EINVAL;
+	}
+	ops = __efivars->ops;
 	status = ops->set_variable(entry->var.VariableName,
 				   &entry->var.VendorGuid,
 				   0, 0, NULL);
@@ -650,13 +672,19 @@ EXPORT_SYMBOL_GPL(efivar_entry_delete);
 int efivar_entry_set(struct efivar_entry *entry, u32 attributes,
 		     unsigned long size, void *data, struct list_head *head)
 {
-	const struct efivar_operations *ops = __efivars->ops;
+	const struct efivar_operations *ops;
 	efi_status_t status;
 	efi_char16_t *name = entry->var.VariableName;
 	efi_guid_t vendor = entry->var.VendorGuid;
 
 	if (down_interruptible(&efivars_lock))
 		return -EINTR;
+
+	if (!__efivars) {
+		up(&efivars_lock);
+		return -EINVAL;
+	}
+	ops = __efivars->ops;
 	if (head && efivar_entry_find(name, vendor, head, false)) {
 		up(&efivars_lock);
 		return -EEXIST;
@@ -687,12 +715,17 @@ static int
 efivar_entry_set_nonblocking(efi_char16_t *name, efi_guid_t vendor,
 			     u32 attributes, unsigned long size, void *data)
 {
-	const struct efivar_operations *ops = __efivars->ops;
+	const struct efivar_operations *ops;
 	efi_status_t status;
 
 	if (down_trylock(&efivars_lock))
 		return -EBUSY;
 
+	if (!__efivars) {
+		up(&efivars_lock);
+		return -EINVAL;
+	}
+
 	status = check_var_size_nonblocking(attributes,
 					    size + ucs2_strsize(name, 1024));
 	if (status != EFI_SUCCESS) {
@@ -700,6 +733,7 @@ efivar_entry_set_nonblocking(efi_char16_t *name, efi_guid_t vendor,
 		return -ENOSPC;
 	}
 
+	ops = __efivars->ops;
 	status = ops->set_variable_nonblocking(name, &vendor, attributes,
 					       size, data);
 
@@ -727,9 +761,13 @@ efivar_entry_set_nonblocking(efi_char16_t *name, efi_guid_t vendor,
 int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
 			  bool block, unsigned long size, void *data)
 {
-	const struct efivar_operations *ops = __efivars->ops;
+	const struct efivar_operations *ops;
 	efi_status_t status;
 
+	if (!__efivars)
+		return -EINVAL;
+
+	ops = __efivars->ops;
 	if (!ops->query_variable_store)
 		return -ENOSYS;
 
@@ -829,13 +867,18 @@ EXPORT_SYMBOL_GPL(efivar_entry_find);
  */
 int efivar_entry_size(struct efivar_entry *entry, unsigned long *size)
 {
-	const struct efivar_operations *ops = __efivars->ops;
+	const struct efivar_operations *ops;
 	efi_status_t status;
 
 	*size = 0;
 
 	if (down_interruptible(&efivars_lock))
 		return -EINTR;
+	if (!__efivars) {
+		up(&efivars_lock);
+		return -EINVAL;
+	}
+	ops = __efivars->ops;
 	status = ops->get_variable(entry->var.VariableName,
 				   &entry->var.VendorGuid, NULL, size, NULL);
 	up(&efivars_lock);
@@ -861,12 +904,14 @@ EXPORT_SYMBOL_GPL(efivar_entry_size);
 int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
 		       unsigned long *size, void *data)
 {
-	const struct efivar_operations *ops = __efivars->ops;
 	efi_status_t status;
 
-	status = ops->get_variable(entry->var.VariableName,
-				   &entry->var.VendorGuid,
-				   attributes, size, data);
+	if (!__efivars)
+		return -EINVAL;
+
+	status = __efivars->ops->get_variable(entry->var.VariableName,
+					      &entry->var.VendorGuid,
+					      attributes, size, data);
 
 	return efi_status_to_err(status);
 }
@@ -882,14 +927,19 @@ EXPORT_SYMBOL_GPL(__efivar_entry_get);
 int efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
 		     unsigned long *size, void *data)
 {
-	const struct efivar_operations *ops = __efivars->ops;
 	efi_status_t status;
 
 	if (down_interruptible(&efivars_lock))
 		return -EINTR;
-	status = ops->get_variable(entry->var.VariableName,
-				   &entry->var.VendorGuid,
-				   attributes, size, data);
+
+	if (!__efivars) {
+		up(&efivars_lock);
+		return -EINVAL;
+	}
+
+	status = __efivars->ops->get_variable(entry->var.VariableName,
+					      &entry->var.VendorGuid,
+					      attributes, size, data);
 	up(&efivars_lock);
 
 	return efi_status_to_err(status);
@@ -921,7 +971,7 @@ EXPORT_SYMBOL_GPL(efivar_entry_get);
 int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
 			      unsigned long *size, void *data, bool *set)
 {
-	const struct efivar_operations *ops = __efivars->ops;
+	const struct efivar_operations *ops;
 	efi_char16_t *name = entry->var.VariableName;
 	efi_guid_t *vendor = &entry->var.VendorGuid;
 	efi_status_t status;
@@ -940,6 +990,11 @@ int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
 	if (down_interruptible(&efivars_lock))
 		return -EINTR;
 
+	if (!__efivars) {
+		err = -EINVAL;
+		goto out;
+	}
+
 	/*
 	 * Ensure that the available space hasn't shrunk below the safe level
 	 */
@@ -956,6 +1011,8 @@ int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
 		}
 	}
 
+	ops = __efivars->ops;
+
 	status = ops->set_variable(name, vendor, attributes, *size, data);
 	if (status != EFI_SUCCESS) {
 		err = efi_status_to_err(status);
-- 
2.19.1


  parent reply index

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-29 17:12 [GIT PULL 00/11] EFI updates Ard Biesheuvel
2018-11-29 17:12 ` [PATCH 01/11] x86/efi: Allocate e820 buffer before calling efi_exit_boot_service Ard Biesheuvel
2018-11-30  7:29   ` Ingo Molnar
2018-11-30  8:26     ` Ard Biesheuvel
2018-11-30  8:36       ` Ingo Molnar
2018-11-30  9:55   ` [tip:efi/core] " tip-bot for Eric Snowberg
2018-11-29 17:12 ` [PATCH 02/11] efi/fdt: Indentation fix Ard Biesheuvel
2018-11-30  7:56   ` [PATCH] efi/fdt: More cleanups Ingo Molnar
2018-11-30  8:31     ` Ard Biesheuvel
2018-11-30  9:48       ` Ingo Molnar
2018-11-30  9:56   ` [tip:efi/core] efi/fdt: Indentation fix tip-bot for Julien Thierry
2018-11-29 17:12 ` [PATCH 03/11] efi/fdt: Simplify get_fdt flow Ard Biesheuvel
2018-11-30  9:57   ` [tip:efi/core] efi/fdt: Simplify the get_fdt() flow tip-bot for Julien Thierry
2018-11-29 17:12 ` [PATCH 04/11] x86/mm/pageattr: Introduce helper function to unmap EFI boot services Ard Biesheuvel
2018-11-30  9:58   ` [tip:efi/core] " tip-bot for Sai Praneeth Prakhya
2018-11-29 17:12 ` [PATCH 05/11] x86/efi: Unmap EFI boot services code/data regions from efi_pgd Ard Biesheuvel
2018-11-30  9:58   ` [tip:efi/core] " tip-bot for Sai Praneeth Prakhya
2018-12-17 18:06     ` Prakhya, Sai Praneeth
2018-12-17 18:10       ` Ard Biesheuvel
2018-12-17 18:42         ` Prakhya, Sai Praneeth
2018-12-17 19:35           ` Ard Biesheuvel
2018-12-17 19:48             ` Prakhya, Sai Praneeth
2018-12-21 17:02               ` Ard Biesheuvel
2018-12-21 17:13                 ` Borislav Petkov
2018-12-21 17:26                   ` Ard Biesheuvel
2018-12-21 19:29                     ` Borislav Petkov
2018-12-22 11:07                       ` Ard Biesheuvel
2019-01-07 15:57                         ` Matt Fleming
2018-12-21 17:52                 ` Prakhya, Sai Praneeth
2018-11-29 17:12 ` [PATCH 06/11] x86/efi: Move efi_<reserve/free>_boot_services() to arch/x86 Ard Biesheuvel
2018-11-30  9:59   ` [tip:efi/core] " tip-bot for Sai Praneeth Prakhya
2018-11-29 17:12 ` [PATCH 07/11] efi/libstub: Disable some warnings for x86{,_64} Ard Biesheuvel
2018-11-30  9:59   ` [tip:efi/core] " tip-bot for Nathan Chancellor
2018-11-29 17:12 ` Ard Biesheuvel [this message]
2018-11-30  8:11   ` [PATCH 08/11] firmware: efi: add NULL pointer checks in efivars api functions Ingo Molnar
2018-11-30  8:37     ` Ard Biesheuvel
2018-11-30  9:56   ` [tip:efi/core] firmware/efi: Add NULL pointer checks in efivars API functions tip-bot for Arend van Spriel
2018-11-29 17:12 ` [PATCH 09/11] efi: permit multiple entries in persistent memreserve data structure Ard Biesheuvel
2018-11-30 10:00   ` [tip:efi/core] efi: Permit " tip-bot for Ard Biesheuvel
2018-11-29 17:12 ` [PATCH 10/11] efi: reduce the amount of memblock reservations for persistent allocations Ard Biesheuvel
2018-11-30  8:38   ` Ingo Molnar
2018-11-30  8:39     ` Ard Biesheuvel
2018-11-30 10:00   ` [tip:efi/core] efi: Reduce " tip-bot for Ard Biesheuvel
2018-11-29 17:12 ` [PATCH 11/11] efi/x86: earlyprintk - Fix infinite loop on some screen widths Ard Biesheuvel
2018-11-30  8:05   ` Ingo Molnar
2018-11-30  8:32     ` Ard Biesheuvel
2018-11-30  9:55   ` [tip:efi/core] x86/earlyprintk/efi: " tip-bot for YiFei Zhu
2018-11-29 18:27 ` [GIT PULL 00/11] EFI updates Prakhya, Sai Praneeth
2018-11-30 12:01   ` Ard Biesheuvel
2018-11-30 18:01     ` Prakhya, Sai Praneeth

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