[linux-yocto] [PATCH] modules: always page-align module section allocations

[zhe.he at windriver.com]

From: Jessica Yu <jeyu at kernel.org>

Some arches (e.g., arm64, x86) have moved towards non-executable
module_alloc() allocations for security hardening reasons. That means
that the module loader will need to set the text section of a module to
executable, regardless of whether or not CONFIG_STRICT_MODULE_RWX is set.

When CONFIG_STRICT_MODULE_RWX=y, module section allocations are always
page-aligned to handle memory rwx permissions. On some arches with
CONFIG_STRICT_MODULE_RWX=n however, when setting the module text to
executable, the BUG_ON() in frob_text() gets triggered since module
section allocations are not page-aligned when CONFIG_STRICT_MODULE_RWX=n.
Since the set_memory_* API works with pages, and since we need to call
set_memory_x() regardless of whether CONFIG_STRICT_MODULE_RWX is set, we
might as well page-align all module section allocations for ease of
managing rwx permissions of module sections (text, rodata, etc).

Fixes: 2eef1399a866 ("modules: fix BUG when load module with rodata=n")
Reported-by: Martin Kaiser <lists at kaiser.cx>
Reported-by: Bartosz Golaszewski <brgl at bgdev.pl>
Tested-by: David Lechner <david at lechnology.com>
Tested-by: Martin Kaiser <martin at kaiser.cx>
Tested-by: Bartosz Golaszewski <bgolaszewski at baylibre.com>
Signed-off-by: Jessica Yu <jeyu at kernel.org>

commit 	38f054d549a869f22a02224cd276a27bf14b6171 upstream

When loading modules with CONFIG_ARCH_HAS_STRICT_MODULE_RWX enabled and
CONFIG_STRICT_MODULE_RWX disabled, the memory allocated for modules would
not be page-aligned and cause the following BUG during frob_text.

------------[ cut here ]------------
kernel BUG at kernel/module.c:1907!
Internal error: Oops - BUG: 0 [#1] ARM
Modules linked in:
CPU: 0 PID: 89 Comm: systemd-modules Not tainted 5.3.0-rc2 #1
Hardware name: ARM-Versatile (Device Tree Support)
PC is at frob_text.constprop.0+0x2c/0x40
LR is at load_module+0x14b4/0x1d28
pc : [<c0082930>]    lr : [<c0084bb0>]    psr: 20000013
sp : ce44fe58  ip : 00000000  fp : 00000000
r10: 00000000  r9 : ce44feb8  r8 : 00000000
r7 : 00000001  r6 : bf00032c  r5 : ce44ff40  r4 : bf000320
r3 : bf000400  r2 : 00000fff  r1 : 00000220  r0 : bf000000
Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 00093177  Table: 0e4c0000  DAC: 00000051
Process systemd-modules (pid: 89, stack limit = 0x9fccc8dc)
Stack: (0xce44fe58 to 0xce450000)
fe40:                                                       00000000 cf1b05b8
fe60: 00000001 ce47cf08 bf002754 c07ae5d8 d0a2a484 bf002060 bf0004f8 00000000
fe80: b6d17910 c017cf1c ce47cf00 d0a29000 ce47cf00 ce44ff34 000014fc 00000000
fea0: 00000000 00000000 bf00025c 00000001 00000000 00000000 6e72656b 00006c65
fec0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
fee0: 00000000 00000000 00000000 00000000 00000000 c0ac9048 7fffffff 00000000
ff00: b6d17910 00000005 0000017b c0009208 ce44e000 00000000 b6ebfe54 c008562c
ff20: 7fffffff 00000000 00000003 cefd28f8 00000001 d0a29000 000014fc 00000000
ff40: d0a292cb d0a29380 d0a29000 000014fc d0a29f0c d0a29d90 d0a29a60 00000520
ff60: 00000710 00000718 00000826 00000000 00000000 00000000 00000708 00000023
ff80: 00000024 0000001c 00000000 00000016 00000000 c0ac9048 0041c620 00000000
ffa0: 00000000 c0009000 0041c620 00000000 00000005 b6d17910 00000000 00000000
ffc0: 0041c620 00000000 00000000 0000017b 0041f078 00000000 004098b0 b6ebfe54
ffe0: bedb6bc8 bedb6bb8 b6d0f91c b6c945a0 60000010 00000005 00000000 00000000
[<c0082930>] (frob_text.constprop.0) from [<c0084bb0>] (load_module+0x14b4/0x1d28)
[<c0084bb0>] (load_module) from [<c008562c>] (sys_finit_module+0xa0/0xc4)
[<c008562c>] (sys_finit_module) from [<c0009000>] (ret_fast_syscall+0x0/0x50)
Exception stack(0xce44ffa8 to 0xce44fff0)
ffa0:                   0041c620 00000000 00000005 b6d17910 00000000 00000000
ffc0: 0041c620 00000000 00000000 0000017b 0041f078 00000000 004098b0 b6ebfe54
ffe0: bedb6bc8 bedb6bb8 b6d0f91c b6c945a0
Code: e7f001f2 e5931008 e1110002 0a000001 (e7f001f2)
---[ end trace e904557128d9aed5 ]---

Signed-off-by: He Zhe <zhe.he at windriver.com>
---
This is for linux-yocto-dev all branches.

 kernel/module.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 5933395..cd8df51 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -64,14 +64,9 @@
 
 /*
  * Modules' sections will be aligned on page boundaries
- * to ensure complete separation of code and data, but
- * only when CONFIG_STRICT_MODULE_RWX=y
+ * to ensure complete separation of code and data
  */
-#ifdef CONFIG_STRICT_MODULE_RWX
 # define debug_align(X) ALIGN(X, PAGE_SIZE)
-#else
-# define debug_align(X) (X)
-#endif
 
 /* If this is set, the section belongs in the init part of the module */
 #define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))
-- 
2.7.4