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authorJinbum Park <jinb.park7@gmail.com>2017-12-12 01:43:57 +0100
committerRussell King <rmk+kernel@armlinux.org.uk>2018-01-21 15:32:20 +0000
commita8e53c151fe7ac52a1c13a6ace0c9e8e0f61260c (patch)
treebdd795b97c9311d45e626e5b90814afcd78567a0 /arch/arm/mm/dump.c
parentd02ca6d76ba7f089706db555ee19f3775bc42740 (diff)
ARM: 8737/1: mm: dump: add checking for writable and executable
Page mappings with full RWX permissions are a security risk. x86, arm64 has an option to walk the page tables and dump any bad pages. (1404d6f13e47 ("arm64: dump: Add checking for writable and exectuable pages")) Add a similar implementation for arm. Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Laura Abbott <labbott@redhat.com> Reviewed-by: Laura Abbott <labbott@redhat.com> Signed-off-by: Jinbum Park <jinb.park7@gmail.com> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/mm/dump.c')
-rw-r--r--arch/arm/mm/dump.c58
1 files changed, 57 insertions, 1 deletions
diff --git a/arch/arm/mm/dump.c b/arch/arm/mm/dump.c
index 43a2beedbbf3..084779c5c893 100644
--- a/arch/arm/mm/dump.c
+++ b/arch/arm/mm/dump.c
@@ -52,6 +52,8 @@ struct pg_state {
unsigned long start_address;
unsigned level;
u64 current_prot;
+ bool check_wx;
+ unsigned long wx_pages;
const char *current_domain;
};
@@ -60,6 +62,8 @@ struct prot_bits {
u64 val;
const char *set;
const char *clear;
+ bool ro_bit;
+ bool nx_bit;
};
static const struct prot_bits pte_bits[] = {
@@ -73,11 +77,13 @@ static const struct prot_bits pte_bits[] = {
.val = L_PTE_RDONLY,
.set = "ro",
.clear = "RW",
+ .ro_bit = true,
}, {
.mask = L_PTE_XN,
.val = L_PTE_XN,
.set = "NX",
.clear = "x ",
+ .nx_bit = true,
}, {
.mask = L_PTE_SHARED,
.val = L_PTE_SHARED,
@@ -141,11 +147,13 @@ static const struct prot_bits section_bits[] = {
.val = L_PMD_SECT_RDONLY | PMD_SECT_AP2,
.set = "ro",
.clear = "RW",
+ .ro_bit = true,
#elif __LINUX_ARM_ARCH__ >= 6
{
.mask = PMD_SECT_APX | PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
.val = PMD_SECT_APX | PMD_SECT_AP_WRITE,
.set = " ro",
+ .ro_bit = true,
}, {
.mask = PMD_SECT_APX | PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
.val = PMD_SECT_AP_WRITE,
@@ -164,6 +172,7 @@ static const struct prot_bits section_bits[] = {
.mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
.val = 0,
.set = " ro",
+ .ro_bit = true,
}, {
.mask = PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
.val = PMD_SECT_AP_WRITE,
@@ -182,6 +191,7 @@ static const struct prot_bits section_bits[] = {
.val = PMD_SECT_XN,
.set = "NX",
.clear = "x ",
+ .nx_bit = true,
}, {
.mask = PMD_SECT_S,
.val = PMD_SECT_S,
@@ -194,6 +204,8 @@ struct pg_level {
const struct prot_bits *bits;
size_t num;
u64 mask;
+ const struct prot_bits *ro_bit;
+ const struct prot_bits *nx_bit;
};
static struct pg_level pg_level[] = {
@@ -226,6 +238,23 @@ static void dump_prot(struct pg_state *st, const struct prot_bits *bits, size_t
}
}
+static void note_prot_wx(struct pg_state *st, unsigned long addr)
+{
+ if (!st->check_wx)
+ return;
+ if ((st->current_prot & pg_level[st->level].ro_bit->mask) ==
+ pg_level[st->level].ro_bit->val)
+ return;
+ if ((st->current_prot & pg_level[st->level].nx_bit->mask) ==
+ pg_level[st->level].nx_bit->val)
+ return;
+
+ WARN_ONCE(1, "arm/mm: Found insecure W+X mapping at address %pS\n",
+ (void *)st->start_address);
+
+ st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
+}
+
static void note_page(struct pg_state *st, unsigned long addr,
unsigned int level, u64 val, const char *domain)
{
@@ -244,6 +273,7 @@ static void note_page(struct pg_state *st, unsigned long addr,
unsigned long delta;
if (st->current_prot) {
+ note_prot_wx(st, addr);
pt_dump_seq_printf(st->seq, "0x%08lx-0x%08lx ",
st->start_address, addr);
@@ -367,6 +397,7 @@ void ptdump_walk_pgd(struct seq_file *m, struct ptdump_info *info)
struct pg_state st = {
.seq = m,
.marker = info->markers,
+ .check_wx = false,
};
walk_pgd(&st, info->mm, info->base_addr);
@@ -379,8 +410,13 @@ static void ptdump_initialize(void)
for (i = 0; i < ARRAY_SIZE(pg_level); i++)
if (pg_level[i].bits)
- for (j = 0; j < pg_level[i].num; j++)
+ for (j = 0; j < pg_level[i].num; j++) {
pg_level[i].mask |= pg_level[i].bits[j].mask;
+ if (pg_level[i].bits[j].ro_bit)
+ pg_level[i].ro_bit = &pg_level[i].bits[j];
+ if (pg_level[i].bits[j].nx_bit)
+ pg_level[i].nx_bit = &pg_level[i].bits[j];
+ }
address_markers[2].start_address = VMALLOC_START;
}
@@ -391,6 +427,26 @@ static struct ptdump_info kernel_ptdump_info = {
.base_addr = 0,
};
+void ptdump_check_wx(void)
+{
+ struct pg_state st = {
+ .seq = NULL,
+ .marker = (struct addr_marker[]) {
+ { 0, NULL},
+ { -1, NULL},
+ },
+ .check_wx = true,
+ };
+
+ walk_pgd(&st, &init_mm, 0);
+ note_page(&st, 0, 0, 0, NULL);
+ if (st.wx_pages)
+ pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n",
+ st.wx_pages);
+ else
+ pr_info("Checked W+X mappings: passed, no W+X pages found\n");
+}
+
static int ptdump_init(void)
{
ptdump_initialize();