| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Sun, 1 Mar 2009 16:11:58 +0200
From: Pekka Paalanen <pq@....fi>
To: Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>
Cc: Pekka Paalanen <pq@....fi>,
Stuart Bennett <stuart@...edesktop.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH 4/7] x86 mmiotrace: fix save/restore page table state
>From baa99e2b32449ec7bf147c234adfa444caecac8a Mon Sep 17 00:00:00 2001
From: Pekka Paalanen <pq@....fi>
Date: Sun, 22 Feb 2009 20:02:43 +0200
Subject: [PATCH] x86 mmiotrace: fix save/restore page table state
Blindly setting _PAGE_PRESENT in disarm_kmmio_fault_page() overlooks the
possibility, that the page was not present when it was armed.
Make arm_kmmio_fault_page() store the previous page presence in struct
kmmio_fault_page and use it on disarm.
This patch was originally written by Stuart Bennett, but Pekka Paalanen
rewrote it a little different.
Cc: Stuart Bennett <stuart@...edesktop.org>
Signed-off-by: Pekka Paalanen <pq@....fi>
---
arch/x86/mm/kmmio.c | 66 ++++++++++++++++++++++++++++++++++-----------------
1 files changed, 44 insertions(+), 22 deletions(-)
diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
index fb1f115..be361eb 100644
--- a/arch/x86/mm/kmmio.c
+++ b/arch/x86/mm/kmmio.c
@@ -32,6 +32,8 @@ struct kmmio_fault_page {
struct list_head list;
struct kmmio_fault_page *release_next;
unsigned long page; /* location of the fault page */
+ bool old_presence; /* page presence prior to arming */
+ bool armed;
/*
* Number of times this page has been registered as a part
@@ -105,8 +107,7 @@ static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long page)
return NULL;
}
-static int set_page_present(unsigned long addr, bool present,
- unsigned int *pglevel)
+static int set_page_presence(unsigned long addr, bool present, bool *old)
{
pteval_t pteval;
pmdval_t pmdval;
@@ -119,20 +120,21 @@ static int set_page_present(unsigned long addr, bool present,
return -1;
}
- if (pglevel)
- *pglevel = level;
-
switch (level) {
case PG_LEVEL_2M:
pmd = (pmd_t *)pte;
- pmdval = pmd_val(*pmd) & ~_PAGE_PRESENT;
+ pmdval = pmd_val(*pmd);
+ *old = !!(pmdval & _PAGE_PRESENT);
+ pmdval &= ~_PAGE_PRESENT;
if (present)
pmdval |= _PAGE_PRESENT;
set_pmd(pmd, __pmd(pmdval));
break;
case PG_LEVEL_4K:
- pteval = pte_val(*pte) & ~_PAGE_PRESENT;
+ pteval = pte_val(*pte);
+ *old = !!(pteval & _PAGE_PRESENT);
+ pteval &= ~_PAGE_PRESENT;
if (present)
pteval |= _PAGE_PRESENT;
set_pte_atomic(pte, __pte(pteval));
@@ -148,19 +150,39 @@ static int set_page_present(unsigned long addr, bool present,
return 0;
}
-/** Mark the given page as not present. Access to it will trigger a fault. */
-static int arm_kmmio_fault_page(unsigned long page, unsigned int *pglevel)
+/*
+ * Mark the given page as not present. Access to it will trigger a fault.
+ *
+ * Struct kmmio_fault_page is protected by RCU and kmmio_lock, but the
+ * protection is ignored here. RCU read lock is assumed held, so the struct
+ * will not disappear unexpectedly. Furthermore, the caller must guarantee,
+ * that double arming the same virtual address (page) cannot occur.
+ *
+ * Double disarming on the other hand is allowed, and may occur when a fault
+ * and mmiotrace shutdown happen simultaneously.
+ */
+static int arm_kmmio_fault_page(struct kmmio_fault_page *f)
{
- int ret = set_page_present(page & PAGE_MASK, false, pglevel);
- WARN_ONCE(ret < 0, KERN_ERR "kmmio arming 0x%08lx failed.\n", page);
+ int ret;
+ WARN_ONCE(f->armed, KERN_ERR "kmmio page already armed.\n");
+ if (f->armed) {
+ pr_warning("kmmio double-arm: page 0x%08lx, ref %d, old %d\n",
+ f->page, f->count, f->old_presence);
+ }
+ ret = set_page_presence(f->page, false, &f->old_presence);
+ WARN_ONCE(ret < 0, KERN_ERR "kmmio arming 0x%08lx failed.\n", f->page);
+ f->armed = true;
return ret;
}
-/** Mark the given page as present. */
-static void disarm_kmmio_fault_page(unsigned long page, unsigned int *pglevel)
+/** Restore the given page to saved presence state. */
+static void disarm_kmmio_fault_page(struct kmmio_fault_page *f)
{
- int ret = set_page_present(page & PAGE_MASK, true, pglevel);
- WARN_ONCE(ret < 0, KERN_ERR "kmmio disarming 0x%08lx failed.\n", page);
+ bool tmp;
+ int ret = set_page_presence(f->page, f->old_presence, &tmp);
+ WARN_ONCE(ret < 0,
+ KERN_ERR "kmmio disarming 0x%08lx failed.\n", f->page);
+ f->armed = false;
}
/*
@@ -207,7 +229,7 @@ int kmmio_handler(struct pt_regs *regs, unsigned long addr)
ctx = &get_cpu_var(kmmio_ctx);
if (ctx->active) {
- disarm_kmmio_fault_page(faultpage->page, NULL);
+ disarm_kmmio_fault_page(faultpage);
if (addr == ctx->addr) {
/*
* On SMP we sometimes get recursive probe hits on the
@@ -249,7 +271,7 @@ int kmmio_handler(struct pt_regs *regs, unsigned long addr)
regs->flags &= ~X86_EFLAGS_IF;
/* Now we set present bit in PTE and single step. */
- disarm_kmmio_fault_page(ctx->fpage->page, NULL);
+ disarm_kmmio_fault_page(ctx->fpage);
/*
* If another cpu accesses the same page while we are stepping,
@@ -288,7 +310,7 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
if (ctx->probe && ctx->probe->post_handler)
ctx->probe->post_handler(ctx->probe, condition, regs);
- arm_kmmio_fault_page(ctx->fpage->page, NULL);
+ arm_kmmio_fault_page(ctx->fpage);
regs->flags &= ~X86_EFLAGS_TF;
regs->flags |= ctx->saved_flags;
@@ -320,19 +342,19 @@ static int add_kmmio_fault_page(unsigned long page)
f = get_kmmio_fault_page(page);
if (f) {
if (!f->count)
- arm_kmmio_fault_page(f->page, NULL);
+ arm_kmmio_fault_page(f);
f->count++;
return 0;
}
- f = kmalloc(sizeof(*f), GFP_ATOMIC);
+ f = kzalloc(sizeof(*f), GFP_ATOMIC);
if (!f)
return -1;
f->count = 1;
f->page = page;
- if (arm_kmmio_fault_page(f->page, NULL)) {
+ if (arm_kmmio_fault_page(f)) {
kfree(f);
return -1;
}
@@ -356,7 +378,7 @@ static void release_kmmio_fault_page(unsigned long page,
f->count--;
BUG_ON(f->count < 0);
if (!f->count) {
- disarm_kmmio_fault_page(f->page, NULL);
+ disarm_kmmio_fault_page(f);
f->release_next = *release_list;
*release_list = f;
}
--
1.6.0.6
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists