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From: Kees Cook <keescook@chromium.org>
To: linux-kernel@vger.kernel.org
Cc: "Kees Cook" <keescook@chromium.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Nicholas Piggin" <npiggin@gmail.com>,
	"Laura Abbott" <labbott@redhat.com>,
	"Mickaël Salaün" <mic@digikod.net>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"David Windsor" <dave@nullcore.net>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Christoph Lameter" <cl@linux.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Christian Borntraeger" <borntraeger@de.ibm.com>,
	"Christoffer Dall" <christoffer.dall@linaro.org>,
	"Dave Kleikamp" <dave.kleikamp@oracle.com>,
	"Jan Kara" <jack@suse.cz>,
	"Luis de Bethencourt" <luisbg@kernel.org>,
	"Marc Zyngier" <marc.zyngier@arm.com>,
	"Rik van Riel" <riel@redhat.com>,
	"Matthew Garrett" <mjg59@google.com>,
	linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org,
	netdev@vger.kernel.org, linux-mm@kvack.org,
	kernel-hardening@lists.openwall.com
Subject: [kernel-hardening] [PATCH 31/38] fork: Provide usercopy whitelisting for task_struct
Date: Wed, 10 Jan 2018 18:03:03 -0800	[thread overview]
Message-ID: <1515636190-24061-32-git-send-email-keescook@chromium.org> (raw)
In-Reply-To: <1515636190-24061-1-git-send-email-keescook@chromium.org>

While the blocked and saved_sigmask fields of task_struct are copied to
userspace (via sigmask_to_save() and setup_rt_frame()), it is always
copied with a static length (i.e. sizeof(sigset_t)).

The only portion of task_struct that is potentially dynamically sized and
may be copied to userspace is in the architecture-specific thread_struct
at the end of task_struct.

cache object allocation:
    kernel/fork.c:
        alloc_task_struct_node(...):
            return kmem_cache_alloc_node(task_struct_cachep, ...);

        dup_task_struct(...):
            ...
            tsk = alloc_task_struct_node(node);

        copy_process(...):
            ...
            dup_task_struct(...)

        _do_fork(...):
            ...
            copy_process(...)

example usage trace:

    arch/x86/kernel/fpu/signal.c:
        __fpu__restore_sig(...):
            ...
            struct task_struct *tsk = current;
            struct fpu *fpu = &tsk->thread.fpu;
            ...
            __copy_from_user(&fpu->state.xsave, ..., state_size);

        fpu__restore_sig(...):
            ...
            return __fpu__restore_sig(...);

    arch/x86/kernel/signal.c:
        restore_sigcontext(...):
            ...
            fpu__restore_sig(...)

This introduces arch_thread_struct_whitelist() to let an architecture
declare specifically where the whitelist should be within thread_struct.
If undefined, the entire thread_struct field is left whitelisted.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: "Mickaël Salaün" <mic@digikod.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Rik van Riel <riel@redhat.com>
---
 arch/Kconfig               | 11 +++++++++++
 include/linux/sched/task.h | 14 ++++++++++++++
 kernel/fork.c              | 22 ++++++++++++++++++++--
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 400b9e1b2f27..8911ff37335a 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -242,6 +242,17 @@ config ARCH_INIT_TASK
 config ARCH_TASK_STRUCT_ALLOCATOR
 	bool
 
+config HAVE_ARCH_THREAD_STRUCT_WHITELIST
+	bool
+	depends on !ARCH_TASK_STRUCT_ALLOCATOR
+	help
+	  An architecture should select this to provide hardened usercopy
+	  knowledge about what region of the thread_struct should be
+	  whitelisted for copying to userspace. Normally this is only the
+	  FPU registers. Specifically, arch_thread_struct_whitelist()
+	  should be implemented. Without this, the entire thread_struct
+	  field in task_struct will be left whitelisted.
+
 # Select if arch has its private alloc_thread_stack() function
 config ARCH_THREAD_STACK_ALLOCATOR
 	bool
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 05b8650f06f5..5be31eb7b266 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -104,6 +104,20 @@ extern int arch_task_struct_size __read_mostly;
 # define arch_task_struct_size (sizeof(struct task_struct))
 #endif
 
+#ifndef CONFIG_HAVE_ARCH_THREAD_STRUCT_WHITELIST
+/*
+ * If an architecture has not declared a thread_struct whitelist we
+ * must assume something there may need to be copied to userspace.
+ */
+static inline void arch_thread_struct_whitelist(unsigned long *offset,
+						unsigned long *size)
+{
+	*offset = 0;
+	/* Handle dynamically sized thread_struct. */
+	*size = arch_task_struct_size - offsetof(struct task_struct, thread);
+}
+#endif
+
 #ifdef CONFIG_VMAP_STACK
 static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
 {
diff --git a/kernel/fork.c b/kernel/fork.c
index 0e086af148f2..5977e691c754 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -458,6 +458,21 @@ static void set_max_threads(unsigned int max_threads_suggested)
 int arch_task_struct_size __read_mostly;
 #endif
 
+static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
+{
+	/* Fetch thread_struct whitelist for the architecture. */
+	arch_thread_struct_whitelist(offset, size);
+
+	/*
+	 * Handle zero-sized whitelist or empty thread_struct, otherwise
+	 * adjust offset to position of thread_struct in task_struct.
+	 */
+	if (unlikely(*size == 0))
+		*offset = 0;
+	else
+		*offset += offsetof(struct task_struct, thread);
+}
+
 void __init fork_init(void)
 {
 	int i;
@@ -466,11 +481,14 @@ void __init fork_init(void)
 #define ARCH_MIN_TASKALIGN	0
 #endif
 	int align = max_t(int, L1_CACHE_BYTES, ARCH_MIN_TASKALIGN);
+	unsigned long useroffset, usersize;
 
 	/* create a slab on which task_structs can be allocated */
-	task_struct_cachep = kmem_cache_create("task_struct",
+	task_struct_whitelist(&useroffset, &usersize);
+	task_struct_cachep = kmem_cache_create_usercopy("task_struct",
 			arch_task_struct_size, align,
-			SLAB_PANIC|SLAB_ACCOUNT, NULL);
+			SLAB_PANIC|SLAB_ACCOUNT,
+			useroffset, usersize, NULL);
 #endif
 
 	/* do the arch specific task caches init */
-- 
2.7.4

  parent reply	other threads:[~2018-01-11  2:03 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-11  2:02 [kernel-hardening] [PATCH v5 00/38] Hardened usercopy whitelisting Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 01/38] usercopy: Remove pointer from overflow report Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 02/38] usercopy: Enhance and rename report_usercopy() Kees Cook
2018-01-11 17:06   ` [kernel-hardening] " Christopher Lameter
2018-01-14 20:57     ` Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 03/38] usercopy: Include offset in hardened usercopy report Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 04/38] lkdtm/usercopy: Adjust test to include an offset to check reporting Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 05/38] stddef.h: Introduce sizeof_field() Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 06/38] usercopy: Prepare for usercopy whitelisting Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 07/38] usercopy: WARN() on slab cache usercopy region violations Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 08/38] usercopy: Allow strict enforcement of whitelists Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 09/38] usercopy: Mark kmalloc caches as usercopy caches Kees Cook
2019-11-12  7:17   ` Jiri Slaby
2019-11-12 21:21     ` Kees Cook
2019-11-14 21:27       ` Kees Cook
2020-01-23  8:14         ` Jiri Slaby
2020-01-27 23:19           ` Kees Cook
2020-01-28  7:58             ` Christian Borntraeger
2020-01-28 23:01               ` Kees Cook
2020-01-29  9:26                 ` Ursula Braun
2020-01-29 16:43                 ` Christopher Lameter
2020-01-29 17:07                   ` Christian Borntraeger
2020-01-29 17:09                     ` Christoph Hellwig
2020-01-29 17:19                       ` Christian Borntraeger
2020-01-30 19:23                         ` Kees Cook
2020-01-31 12:03                           ` Jann Horn
2020-02-01 17:56                             ` Kees Cook
2020-02-01 19:27                               ` Jann Horn
2020-02-03  7:46                                 ` Matthew Wilcox
2020-02-03 17:41                                   ` Christoph Hellwig
2020-02-03 17:20                               ` Christopher Lameter
2020-04-07  8:00                             ` Vlastimil Babka
2020-04-07 11:05                               ` Christian Borntraeger
2020-04-20  7:53                               ` Jiri Slaby
2020-04-20 17:43                                 ` Kees Cook
2020-02-03 17:38                           ` Christoph Hellwig
2020-02-03 17:36                         ` Christoph Hellwig
2018-01-11  2:02 ` [kernel-hardening] [PATCH 10/38] dcache: Define usercopy region in dentry_cache slab cache Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 11/38] vfs: Define usercopy region in names_cache slab caches Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 12/38] vfs: Copy struct mount.mnt_id to userspace using put_user() Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 13/38] ext4: Define usercopy region in ext4_inode_cache slab cache Kees Cook
2018-01-11 17:01   ` [kernel-hardening] " Theodore Ts'o
2018-01-11 23:05     ` Kees Cook
2018-01-14 22:34       ` Matthew Wilcox
2018-01-11  2:02 ` [kernel-hardening] [PATCH 14/38] ext2: Define usercopy region in ext2_inode_cache " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 15/38] jfs: Define usercopy region in jfs_ip " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 16/38] befs: Define usercopy region in befs_inode_cache " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 17/38] exofs: Define usercopy region in exofs_inode_cache " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 18/38] orangefs: Define usercopy region in orangefs_inode_cache " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 19/38] ufs: Define usercopy region in ufs_inode_cache " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 20/38] vxfs: Define usercopy region in vxfs_inode " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 21/38] cifs: Define usercopy region in cifs_request " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 22/38] scsi: Define usercopy region in scsi_sense_cache " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 23/38] net: Define usercopy region in struct proto " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 24/38] ip: Define usercopy region in IP " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 25/38] caif: Define usercopy region in caif " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 26/38] sctp: Define usercopy region in SCTP " Kees Cook
2018-01-11  2:02 ` [kernel-hardening] [PATCH 27/38] sctp: Copy struct sctp_sock.autoclose to userspace using put_user() Kees Cook
2018-01-18 21:31   ` [kernel-hardening] " Laura Abbott
2018-01-18 21:36     ` Kees Cook
2018-01-11  2:03 ` [kernel-hardening] [PATCH 28/38] net: Restrict unwhitelisted proto caches to size 0 Kees Cook
2018-01-11  2:03 ` [kernel-hardening] [PATCH 29/38] fork: Define usercopy region in mm_struct slab caches Kees Cook
2018-01-11  2:03 ` [kernel-hardening] [PATCH 30/38] fork: Define usercopy region in thread_stack " Kees Cook
2018-01-11  2:03 ` Kees Cook [this message]
2018-01-11  2:03 ` [kernel-hardening] [PATCH 32/38] x86: Implement thread_struct whitelist for hardened usercopy Kees Cook
2018-01-11  2:03 ` [kernel-hardening] [PATCH 33/38] arm64: " Kees Cook
2018-01-15 12:24   ` [kernel-hardening] " Dave P Martin
2018-01-15 20:06     ` Kees Cook
2018-01-16 12:33       ` Dave Martin
2018-03-26 16:22       ` Dave Martin
2018-03-26 17:41         ` Kees Cook
2018-03-27 12:32           ` Dave Martin
2018-01-11  2:03 ` [kernel-hardening] [PATCH 34/38] arm: " Kees Cook
2018-01-11 10:24   ` [kernel-hardening] " Russell King - ARM Linux
2018-01-11 23:21     ` Kees Cook
2018-01-11  2:03 ` [kernel-hardening] [PATCH 35/38] kvm: whitelist struct kvm_vcpu_arch Kees Cook
2018-01-11  2:03 ` [kernel-hardening] [PATCH 36/38] kvm: x86: fix KVM_XEN_HVM_CONFIG ioctl Kees Cook
2018-01-11  2:03 ` [kernel-hardening] [PATCH 37/38] usercopy: Restrict non-usercopy caches to size 0 Kees Cook
2018-01-11  2:03 ` [kernel-hardening] [PATCH 38/38] lkdtm: Update usercopy tests for whitelisting Kees Cook
2018-02-19 16:55 ` [PATCH] signals: Move put_compat_sigset to compat.h to silence hardened usercopy Matt Redfearn
2018-02-19 23:55   ` Kees Cook
2018-03-02 21:40     ` James Hogan

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