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

Fri Aug 16 08:29:07 PDT 2019

[[linux-yocto] [PATCH] modules: always page-align module section allocations] On 16/08/2019 (Fri 15:36) zhe.he at windriver.com wrote:

It helps maintainers if the version is embedded in the subject, like:

  [PATCH v4.18] modules: always page-align module section....

> 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

Normally we put this right at the top of the long log.  Also this commit
ID appears bogus - it does not exist in mainline.

Also it seems very odd that the block of Signed-off lines are stuck in
the middle of the long log.

> 
> 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.

The version information is important, and shouldnt be hidden down here.
If you put it within the [PATCH ....] square bracket section, the
maintainer/merger person will see it and the "git am" will throw it away
once applied.

Paul.
--

> 
>  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
> 
> -- 
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