All of lore.kernel.org
 help / color / mirror / Atom feed
From: Russell Currey <ruscur@russell.cc>
To: linuxppc-dev@lists.ozlabs.org
Cc: ajd@linux.ibm.com, kernel-hardening@lists.openwall.com,
	npiggin@gmail.com, joel@jms.id.au,
	Russell Currey <ruscur@russell.cc>,
	dja@axtens.net
Subject: [PATCH v6 2/7] powerpc/kprobes: Mark newly allocated probes as RO
Date: Tue, 10 Mar 2020 12:03:33 +1100	[thread overview]
Message-ID: <20200310010338.21205-3-ruscur@russell.cc> (raw)
In-Reply-To: <20200310010338.21205-1-ruscur@russell.cc>

With CONFIG_STRICT_KERNEL_RWX=y and CONFIG_KPROBES=y, there will be one
W+X page at boot by default.  This can be tested with
CONFIG_PPC_PTDUMP=y and CONFIG_PPC_DEBUG_WX=y set, and checking the
kernel log during boot.

powerpc doesn't implement its own alloc() for kprobes like other
architectures do, but we couldn't immediately mark RO anyway since we do
a memcpy to the page we allocate later.  After that, nothing should be
allowed to modify the page, and write permissions are removed well
before the kprobe is armed.

The memcpy() would fail if >1 probes were allocated, so use
patch_instruction() instead which is safe for RO.

Reviewed-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/kprobes.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 2d27ec4feee4..bfab91ded234 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -24,6 +24,8 @@
 #include <asm/sstep.h>
 #include <asm/sections.h>
 #include <linux/uaccess.h>
+#include <linux/set_memory.h>
+#include <linux/vmalloc.h>
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -102,6 +104,16 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
 	return addr;
 }
 
+void *alloc_insn_page(void)
+{
+	void *page = vmalloc_exec(PAGE_SIZE);
+
+	if (page)
+		set_memory_ro((unsigned long)page, 1);
+
+	return page;
+}
+
 int arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;
@@ -124,11 +136,8 @@ int arch_prepare_kprobe(struct kprobe *p)
 	}
 
 	if (!ret) {
-		memcpy(p->ainsn.insn, p->addr,
-				MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+		patch_instruction(p->ainsn.insn, *p->addr);
 		p->opcode = *p->addr;
-		flush_icache_range((unsigned long)p->ainsn.insn,
-			(unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
 	}
 
 	p->ainsn.boostable = 0;
-- 
2.25.1


WARNING: multiple messages have this Message-ID (diff)
From: Russell Currey <ruscur@russell.cc>
To: linuxppc-dev@lists.ozlabs.org
Cc: Russell Currey <ruscur@russell.cc>,
	christophe.leroy@c-s.fr, joel@jms.id.au, mpe@ellerman.id.au,
	ajd@linux.ibm.com, dja@axtens.net, npiggin@gmail.com,
	kernel-hardening@lists.openwall.com
Subject: [PATCH v6 2/7] powerpc/kprobes: Mark newly allocated probes as RO
Date: Tue, 10 Mar 2020 12:03:33 +1100	[thread overview]
Message-ID: <20200310010338.21205-3-ruscur@russell.cc> (raw)
In-Reply-To: <20200310010338.21205-1-ruscur@russell.cc>

With CONFIG_STRICT_KERNEL_RWX=y and CONFIG_KPROBES=y, there will be one
W+X page at boot by default.  This can be tested with
CONFIG_PPC_PTDUMP=y and CONFIG_PPC_DEBUG_WX=y set, and checking the
kernel log during boot.

powerpc doesn't implement its own alloc() for kprobes like other
architectures do, but we couldn't immediately mark RO anyway since we do
a memcpy to the page we allocate later.  After that, nothing should be
allowed to modify the page, and write permissions are removed well
before the kprobe is armed.

The memcpy() would fail if >1 probes were allocated, so use
patch_instruction() instead which is safe for RO.

Reviewed-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/kprobes.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 2d27ec4feee4..bfab91ded234 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -24,6 +24,8 @@
 #include <asm/sstep.h>
 #include <asm/sections.h>
 #include <linux/uaccess.h>
+#include <linux/set_memory.h>
+#include <linux/vmalloc.h>
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -102,6 +104,16 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
 	return addr;
 }
 
+void *alloc_insn_page(void)
+{
+	void *page = vmalloc_exec(PAGE_SIZE);
+
+	if (page)
+		set_memory_ro((unsigned long)page, 1);
+
+	return page;
+}
+
 int arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;
@@ -124,11 +136,8 @@ int arch_prepare_kprobe(struct kprobe *p)
 	}
 
 	if (!ret) {
-		memcpy(p->ainsn.insn, p->addr,
-				MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+		patch_instruction(p->ainsn.insn, *p->addr);
 		p->opcode = *p->addr;
-		flush_icache_range((unsigned long)p->ainsn.insn,
-			(unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
 	}
 
 	p->ainsn.boostable = 0;
-- 
2.25.1


  parent reply	other threads:[~2020-03-10  1:09 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-10  1:03 [PATCH v6 0/7] set_memory() routines and STRICT_MODULE_RWX Russell Currey
2020-03-10  1:03 ` Russell Currey
2020-03-10  1:03 ` [PATCH v6 1/7] powerpc/mm: Implement set_memory() routines Russell Currey
2020-03-10  1:03   ` Russell Currey
2020-03-11  6:03   ` Daniel Axtens
2020-03-11  6:03     ` Daniel Axtens
2020-03-31  1:49     ` Russell Currey
2020-03-31  1:49       ` Russell Currey
2020-03-10  1:03 ` Russell Currey [this message]
2020-03-10  1:03   ` [PATCH v6 2/7] powerpc/kprobes: Mark newly allocated probes as RO Russell Currey
2020-03-10  1:03 ` [PATCH v6 3/7] powerpc/mm/ptdump: debugfs handler for W+X checks at runtime Russell Currey
2020-03-10  1:03   ` Russell Currey
2020-03-10  1:03 ` [PATCH v6 4/7] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX Russell Currey
2020-03-10  1:03   ` Russell Currey
2020-03-10  1:03 ` [PATCH v6 5/7] powerpc/configs: Enable STRICT_MODULE_RWX in skiroot_defconfig Russell Currey
2020-03-10  1:03   ` Russell Currey
2020-03-10  1:03 ` [PATCH v6 6/7] powerpc/mm: implement set_memory_attr() Russell Currey
2020-03-10  1:03   ` Russell Currey
2020-03-11  6:09   ` Daniel Axtens
2020-03-11  6:09     ` Daniel Axtens
2020-03-10  1:03 ` [PATCH v6 7/7] powerpc/32: use set_memory_attr() Russell Currey
2020-03-10  1:03   ` Russell Currey

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200310010338.21205-3-ruscur@russell.cc \
    --to=ruscur@russell.cc \
    --cc=ajd@linux.ibm.com \
    --cc=dja@axtens.net \
    --cc=joel@jms.id.au \
    --cc=kernel-hardening@lists.openwall.com \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=npiggin@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.