[PATCH v2] modules: fix BUG when load module with rodata=n

Yang Yingliang
2019-06-20T01:58:44Z

When loading a module with rodata=n, it causes an executing
NX-protected page BUG.

[ 32.379191] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
[ 32.382917] BUG: unable to handle page fault for address: ffffffffc0005000
[ 32.385947] #PF: supervisor instruction fetch in kernel mode
[ 32.387662] #PF: error_code(0x0011) - permissions violation
[ 32.389352] PGD 240c067 P4D 240c067 PUD 240e067 PMD 421a52067 PTE 8000000421a53063
[ 32.391396] Oops: 0011 [#1] SMP PTI
[ 32.392478] CPU: 7 PID: 2697 Comm: insmod Tainted: G O 5.2.0-rc5+ #202
[ 32.394588] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
[ 32.398157] RIP: 0010:ko_test_init+0x0/0x1000 [ko_test]
[ 32.399662] Code: Bad RIP value.
[ 32.400621] RSP: 0018:ffffc900029f3ca8 EFLAGS: 00010246
[ 32.402171] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 32.404332] RDX: 00000000000004c7 RSI: 0000000000000cc0 RDI: ffffffffc0005000
[ 32.406347] RBP: ffffffffc0005000 R08: ffff88842fbebc40 R09: ffffffff810ede4a
[ 32.408392] R10: ffffea00108e3480 R11: 0000000000000000 R12: ffff88842bee21a0
[ 32.410472] R13: 0000000000000001 R14: 0000000000000001 R15: ffffc900029f3e78
[ 32.412609] FS: 00007fb4f0c0a700(0000) GS:ffff88842fbc0000(0000) knlGS:0000000000000000
[ 32.414722] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 32.416290] CR2: ffffffffc0004fd6 CR3: 0000000421a90004 CR4: 0000000000020ee0
[ 32.418471] Call Trace:
[ 32.419136] do_one_initcall+0x41/0x1df
[ 32.420199] ? _cond_resched+0x10/0x40
[ 32.421433] ? kmem_cache_alloc_trace+0x36/0x160
[ 32.422827] do_init_module+0x56/0x1f7
[ 32.423946] load_module+0x1e67/0x2580
[ 32.424947] ? __alloc_pages_nodemask+0x150/0x2c0
[ 32.426413] ? map_vm_area+0x2d/0x40
[ 32.427530] ? __vmalloc_node_range+0x1ef/0x260
[ 32.428850] ? __do_sys_init_module+0x135/0x170
[ 32.430060] ? _cond_resched+0x10/0x40
[ 32.431249] __do_sys_init_module+0x135/0x170
[ 32.432547] do_syscall_64+0x43/0x120
[ 32.433853] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Because if rodata=n, set_memory_x() cann't be called, fix this by
calling set_memory_x in complete_formation();

v1 -> v2:
Remove empty lines between the frob_* calls.

Fixes: f2c65fb3221a ("x86/modules: Avoid breaking W^X while loading modules")
Suggested-by: Jian Cheng <cj.chengjian@huawei.com>
Reviewed-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
kernel/module.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 80c7c09584cf..c3ae34c11c9f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1949,13 +1949,9 @@ void module_enable_ro(const struct module *mod, bool after_init)
set_vm_flush_reset_perms(mod->core_layout.base);
set_vm_flush_reset_perms(mod->init_layout.base);
frob_text(&mod->core_layout, set_memory_ro);
- frob_text(&mod->core_layout, set_memory_x);

frob_rodata(&mod->core_layout, set_memory_ro);
-
frob_text(&mod->init_layout, set_memory_ro);
- frob_text(&mod->init_layout, set_memory_x);
-
frob_rodata(&mod->init_layout, set_memory_ro);

if (after_init)
@@ -2018,6 +2014,12 @@ void set_all_modules_text_ro(void)
static void module_enable_nx(const struct module *mod) { }
#endif

+static void module_enable_x(const struct module *mod)
+{
+ frob_text(&mod->core_layout, set_memory_x);
+ frob_text(&mod->init_layout, set_memory_x);
+}
+
#ifdef CONFIG_LIVEPATCH
/*
* Persist Elf information about a module. Copy the Elf header,
@@ -3616,6 +3618,7 @@ static int complete_formation(struct module *mod, struct load_info *info)

module_enable_ro(mod, false);
module_enable_nx(mod);
+ module_enable_x(mod);

/* Mark state as coming so strong_try_module_get() ignores us,
* but kallsyms etc. can see us. */
--
2.17.1