[PATCH 4.14 033/146] x86/mm/dump_pagetables: Check user space page table for WX pages

Greg Kroah-Hartman
2018-01-01T14:42:47Z

From: Thomas Gleixner <tglx@linutronix.de>

commit b4bf4f924b1d7bade38fd51b2e401d20d0956e4d upstream.

ptdump_walk_pgd_level_checkwx() checks the kernel page table for WX pages,
but does not check the PAGE_TABLE_ISOLATION user space page table.

Restructure the code so that dmesg output is selected by an explicit
argument and not implicit via checking the pgd argument for !NULL.

Add the check for the user space page table.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/include/asm/pgtable.h | 1 +
arch/x86/mm/debug_pagetables.c | 2 +-
arch/x86/mm/dump_pagetables.c | 30 +++++++++++++++++++++++++-----
3 files changed, 27 insertions(+), 6 deletions(-)

--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -28,6 +28,7 @@ extern pgd_t early_top_pgt[PTRS_PER_PGD]
int __init __early_make_pgtable(unsigned long address, pmdval_t pmd);

void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd);
+void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd);
void ptdump_walk_pgd_level_checkwx(void);

#ifdef CONFIG_DEBUG_WX
--- a/arch/x86/mm/debug_pagetables.c
+++ b/arch/x86/mm/debug_pagetables.c
@@ -5,7 +5,7 @@

static int ptdump_show(struct seq_file *m, void *v)
{
- ptdump_walk_pgd_level(m, NULL);
+ ptdump_walk_pgd_level_debugfs(m, NULL);
return 0;
}

--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -476,7 +476,7 @@ static inline bool is_hypervisor_range(i
}

static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
- bool checkwx)
+ bool checkwx, bool dmesg)
{
#ifdef CONFIG_X86_64
pgd_t *start = (pgd_t *) &init_top_pgt;
@@ -489,7 +489,7 @@ static void ptdump_walk_pgd_level_core(s

if (pgd) {
start = pgd;
- st.to_dmesg = true;
+ st.to_dmesg = dmesg;
}

st.check_wx = checkwx;
@@ -527,13 +527,33 @@ static void ptdump_walk_pgd_level_core(s

void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
{
- ptdump_walk_pgd_level_core(m, pgd, false);
+ ptdump_walk_pgd_level_core(m, pgd, false, true);
+}
+
+void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd)
+{
+ ptdump_walk_pgd_level_core(m, pgd, false, false);
+}
+EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs);
+
+static void ptdump_walk_user_pgd_level_checkwx(void)
+{
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+ pgd_t *pgd = (pgd_t *) &init_top_pgt;
+
+ if (!static_cpu_has(X86_FEATURE_PTI))
+ return;
+
+ pr_info("x86/mm: Checking user space page tables\n");
+ pgd = kernel_to_user_pgdp(pgd);
+ ptdump_walk_pgd_level_core(NULL, pgd, true, false);
+#endif
}
-EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level);

void ptdump_walk_pgd_level_checkwx(void)
{
- ptdump_walk_pgd_level_core(NULL, NULL, true);
+ ptdump_walk_pgd_level_core(NULL, NULL, true, false);
+ ptdump_walk_user_pgd_level_checkwx();
}

static int __init pt_dump_init(void)