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Message-Id: <60B48C52-12A6-4810-8C8C-9CC1C1E77E68@toblux.com>
Date: Sat, 14 Sep 2024 01:32:19 +0200
From: Thorsten Blum <thorsten.blum@...lux.com>
To: Nathan Chancellor <nathan@...nel.org>
Cc: kees@...nel.org,
gustavoars@...nel.org,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
mcgrof@...nel.org,
linux-hardening@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v2] params: Annotate struct module_param_attrs with
__counted_by()
Hi Nathan,
> On 13. Sep 2024, at 18:46, Nathan Chancellor <nathan@...nel.org> wrote:
>
> Hi Thorsten,
>
> On Mon, Sep 09, 2024 at 06:27:26PM +0200, Thorsten Blum wrote:
>> Add the __counted_by compiler attribute to the flexible array member
>> attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
>> CONFIG_FORTIFY_SOURCE.
>>
>> Increment num before adding a new param_attribute to the attrs array and
>> adjust the array index accordingly. Increment num immediately after the
>> first reallocation such that the reallocation for the NULL terminator
>> only needs to add 1 (instead of 2) to mk->mp->num.
>>
>> Use struct_size() instead of manually calculating the size for the
>> reallocation.
>>
>> Use krealloc_array() for the additional NULL terminator.
>>
>> Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
>> ---
>> Changes in v2:
>> - Use krealloc_array() as suggested by Andy Shevchenko
>> - Link to v1: https://lore.kernel.org/linux-kernel/20240823123300.37574-1-thorsten.blum@toblux.com/
>> ---
>> kernel/params.c | 29 +++++++++++++----------------
>> 1 file changed, 13 insertions(+), 16 deletions(-)
>>
>> diff --git a/kernel/params.c b/kernel/params.c
>> index 2e447f8ae183..5f6643676697 100644
>> --- a/kernel/params.c
>> +++ b/kernel/params.c
>> @@ -551,7 +551,7 @@ struct module_param_attrs
>> {
>> unsigned int num;
>> struct attribute_group grp;
>> - struct param_attribute attrs[];
>> + struct param_attribute attrs[] __counted_by(num);
>> };
>>
>> #ifdef CONFIG_SYSFS
>> @@ -651,35 +651,32 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
>> }
>>
>> /* Enlarge allocations. */
>> - new_mp = krealloc(mk->mp,
>> - sizeof(*mk->mp) +
>> - sizeof(mk->mp->attrs[0]) * (mk->mp->num + 1),
>> + new_mp = krealloc(mk->mp, struct_size(mk->mp, attrs, mk->mp->num + 1),
>> GFP_KERNEL);
>> if (!new_mp)
>> return -ENOMEM;
>> mk->mp = new_mp;
>> + mk->mp->num++;
>>
>> /* Extra pointer for NULL terminator */
>> - new_attrs = krealloc(mk->mp->grp.attrs,
>> - sizeof(mk->mp->grp.attrs[0]) * (mk->mp->num + 2),
>> - GFP_KERNEL);
>> + new_attrs = krealloc_array(mk->mp->grp.attrs, mk->mp->num + 1,
>> + sizeof(mk->mp->grp.attrs[0]), GFP_KERNEL);
>> if (!new_attrs)
>> return -ENOMEM;
>> mk->mp->grp.attrs = new_attrs;
>>
>> /* Tack new one on the end. */
>> - memset(&mk->mp->attrs[mk->mp->num], 0, sizeof(mk->mp->attrs[0]));
>> - sysfs_attr_init(&mk->mp->attrs[mk->mp->num].mattr.attr);
>> - mk->mp->attrs[mk->mp->num].param = kp;
>> - mk->mp->attrs[mk->mp->num].mattr.show = param_attr_show;
>> + memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0]));
>> + sysfs_attr_init(&mk->mp->attrs[mk->mp->num - 1].mattr.attr);
>> + mk->mp->attrs[mk->mp->num - 1].param = kp;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.show = param_attr_show;
>> /* Do not allow runtime DAC changes to make param writable. */
>> if ((kp->perm & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
>> - mk->mp->attrs[mk->mp->num].mattr.store = param_attr_store;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.store = param_attr_store;
>> else
>> - mk->mp->attrs[mk->mp->num].mattr.store = NULL;
>> - mk->mp->attrs[mk->mp->num].mattr.attr.name = (char *)name;
>> - mk->mp->attrs[mk->mp->num].mattr.attr.mode = kp->perm;
>> - mk->mp->num++;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.store = NULL;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.attr.name = (char *)name;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.attr.mode = kp->perm;
>>
>> /* Fix up all the pointers, since krealloc can move us */
>> for (i = 0; i < mk->mp->num; i++)
>> --
>> 2.46.0
>>
>
> I just bisected this change to a fortify failure that I see with a
> couple different ARM configurations when built with a version of clang
> that supports __counted_by(). I can reproduce this with:
>
> $ curl -LSso .config https://gist.github.com/nathanchance/6df4bd2ab4c4418020b3ed5417ef4f80/raw/758abf666dfe8c76e0f16735f336849ea47ef791/.config
>
> $ make -skj"$(nproc)" ARCH=arm LLVM=1 olddefconfig zImage
>
> $ curl -LSs https://github.com/ClangBuiltLinux/boot-utils/releases/download/20230707-182910/arm-rootfs.cpio.zst | zstd -d >rootfs.cpio
>
> $ qemu-system-arm \
> -display none \
> -nodefaults \
> -no-reboot \
> -machine virt \
> -append 'console=ttyAMA0 earlycon' \
> -kernel arch/arm/boot/zImage \
> -initrd rootfs.cpio \
> -m 512m \
> -serial mon:stdio
> [ 0.000000] Booting Linux on physical CPU 0x0
> [ 0.000000] Linux version 6.11.0-rc4+ (nathan@...lio-3990X) (ClangBuiltLinux clang version 19.1.0-rc4 (https://github.com/llvm/llvm-project.git 0c641568515a797473394694f05937e1f1913d87), ClangBuiltLinux LLD 19.1.0 (https://github.com/llvm/llvm-project.git 0c641568515a797473394694f05937e1f1913d87)) #1 SMP Fri Sep 13 09:36:38 MST 2024
> ...
> [ 0.623959] ------------[ cut here ]------------
> [ 0.624158] WARNING: CPU: 0 PID: 1 at lib/string_helpers.c:1030 __fortify_report+0x64/0x6c
> [ 0.625050] memset: detected buffer overflow: 32 byte write of buffer size 0
> [ 0.625297] Modules linked in:
> [ 0.625712] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.11.0-rc4+ #1
> [ 0.626008] Hardware name: Generic DT based system
> [ 0.626274] Call trace:
> [ 0.626342] unwind_backtrace from show_stack+0x28/0x2c
> [ 0.626690] show_stack from dump_stack_lvl+0x34/0x70
> [ 0.626936] dump_stack_lvl from __warn+0xe0/0x200
> [ 0.627100] __warn from warn_slowpath_fmt+0xc8/0x194
> [ 0.627335] warn_slowpath_fmt from __fortify_report+0x64/0x6c
> [ 0.627551] __fortify_report from __fortify_panic+0x8/0xc
> [ 0.627739] __fortify_panic from add_sysfs_param+0x224/0x228
> [ 0.627927] add_sysfs_param from kernel_add_sysfs_param+0x5c/0xa0
> [ 0.628206] kernel_add_sysfs_param from param_sysfs_builtin+0xf4/0x130
> [ 0.628412] param_sysfs_builtin from param_sysfs_builtin_init+0x30/0x38
> [ 0.628649] param_sysfs_builtin_init from do_one_initcall+0xd0/0x2d4
> [ 0.628869] do_one_initcall from do_initcall_level+0x9c/0x104
> [ 0.629068] do_initcall_level from do_initcalls+0x74/0xb0
> [ 0.629254] do_initcalls from kernel_init_freeable+0x10c/0x158
> [ 0.629452] kernel_init_freeable from kernel_init+0x20/0x1cc
> [ 0.629654] kernel_init from ret_from_fork+0x14/0x28
> [ 0.629872] Exception stack(0xe080dfb0 to 0xe080dff8)
> [ 0.630108] dfa0: 00000000 00000000 00000000 00000000
> [ 0.630391] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.630656] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 0.631064] ---[ end trace 0000000000000000 ]---
> [ 0.631800] ------------[ cut here ]------------
> [ 0.631989] kernel BUG at lib/string_helpers.c:1037!
> [ 0.632175] Internal error: Oops - BUG: 0 [#1] SMP ARM
> [ 0.632472] Modules linked in:
> [ 0.632761] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W 6.11.0-rc4+ #1
> [ 0.633077] Tainted: [W]=WARN
> [ 0.633186] Hardware name: Generic DT based system
> [ 0.633357] PC is at __fortify_panic+0x8/0xc
> [ 0.633521] LR is at __warn+0x16c/0x200
> [ 0.633668] pc : [<c0f6daa8>] lr : [<c035300c>] psr: 60000013
> [ 0.633878] sp : e080db98 ip : 00000000 fp : e080dbb8
> [ 0.634059] r10: 6e72656b r9 : 006c656e r8 : c1000009
> [ 0.634240] r7 : fffffff4 r6 : c135947c r5 : c13d5ebc r4 : c2466f00
> [ 0.634470] r3 : 00000200 r2 : 00000000 r1 : 244cee50 r0 : 244cee50
> [ 0.634738] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
> [ 0.634987] Control: 10c5387d Table: 423ec06a DAC: 00000051
> [ 0.635206] Register r0 information: non-paged memory
> [ 0.635559] Register r1 information: non-paged memory
> [ 0.635745] Register r2 information: NULL pointer
> [ 0.635917] Register r3 information: non-paged memory
> [ 0.636100] Register r4 information: slab kmalloc-64 start c2466f00 pointer offset 0 size 64
> [ 0.636772] Register r5 information: non-slab/vmalloc memory
> [ 0.637001] Register r6 information: non-slab/vmalloc memory
> [ 0.637205] Register r7 information: non-paged memory
> [ 0.637385] Register r8 information: non-slab/vmalloc memory
> [ 0.637597] Register r9 information: non-paged memory
> [ 0.637791] Register r10 information: non-paged memory
> [ 0.637977] Register r11 information: 2-page vmalloc region starting at 0xe080c000 allocated at copy_process+0x17c/0xf18
> [ 0.638382] Register r12 information: NULL pointer
> [ 0.638569] Process swapper/0 (pid: 1, stack limit = 0x8a022d6d)
> [ 0.639040] Stack: (0xe080db98 to 0xe080e000)
> [ 0.639194] db80: e080dbb8 c037f5f8
> [ 0.639462] dba0: c2466f00 c13d5ebc 00000000 c1000009 e080dbd8 6e72656b e080dbd0 c151d860
> [ 0.639728] dbc0: c13d5ebc c13d6dbc 00000000 6e72656b e080dc38 c151d6d8 6e72656b 00006c65
> [ 0.639993] dbe0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.640261] dc00: 00000000 00000000 00000000 00000000 00000000 00000000 244cee50 c1655918
> [ 0.640531] dc20: c215c200 c21f9300 c170f458 c151d4f8 00000000 00000000 e080dc40 c151d528
> [ 0.640795] dc40: e080df40 c0302398 5e4e6cd4 ef580029 00000000 00000000 00000000 00000000
> [ 0.641067] dc60: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.641330] dc80: 00000000 00000000 00000000 00000000 ffffffff 00000000 c18926ac 00000080
> [ 0.641599] dca0: 000000b0 c061cb68 debbd794 debbd794 00000000 c21fd000 e080dce8 c061cb68
> [ 0.641863] dcc0: 244cee50 00000001 00000801 debbd794 00000000 00000801 c1892640 00000000
> [ 0.642126] dce0: c1893440 e080ddd0 e080ddb0 c061e2ec deb63e40 deb63e5c 00000000 00052cc0
> [ 0.642390] dd00: 00000001 00000001 000000b0 00000001 00000000 00000000 00000000 00000064
> [ 0.642657] dd20: 0000006c 00000080 00000001 e080ddd0 00000000 00000000 00000000 00000001
> [ 0.642923] dd40: 00000000 00000000 00000000 00000001 00000000 00000000 00000001 00000000
> [ 0.643187] dd60: c1892930 00000000 00000000 244cee50 00000000 00000000 00000000 00000000
> [ 0.643451] dd80: 00000801 7ffe0000 c1892640 c0b3c530 244cee50 00000000 00052cc0 00000001
> [ 0.643724] dda0: 00000008 00000001 00052cc0 00000000 e080de08 c061cddc 00000820 c0775f50
> [ 0.643992] ddc0: 00000000 c215c200 00000000 00052cc0 c1893440 00000000 c1893440 244cee50
> [ 0.644259] dde0: 00000020 debbd794 7ffe0000 c062c97c c21329c0 debbd794 0000000e 00000020
> [ 0.644532] de00: 00000080 7ffe0000 e080de40 c062c97c c20a763c 00000020 e080de28 c0f74fc0
> [ 0.644800] de20: 244cee50 00000000 00000080 c2133e80 00000000 7fff0000 c21329c0 deb64100
> [ 0.645066] de40: e080dea0 c062a584 c21c1180 c17cb818 0fffffff 00000001 e080ded4 c0f655d8
> [ 0.645330] de60: 00000000 00000001 c2132a48 ffffffff 00000000 c0f43544 ffff0a01 c0f71f18
> [ 0.645592] de80: e080df20 c0f71f18 244cee50 c21c1180 00000cc0 e080ded4 00000079 00000000
> [ 0.645857] dea0: 0fffffff 00000001 00000000 c0f43544 c071ca3c 00000003 00000dc0 00000000
> [ 0.646121] dec0: 00000cc0 00000000 0003ffff 80000053 c21fd66c c17cb818 00000000 00000000
> [ 0.646121] dec0: 00000cc0 00000000 0003ffff 80000053 c21fd66c c17cb818 00000000 00000000
> [ 0.646391] dee0: 00000000 00000000 000000c0 c13d6dbc 00000000 c037e2ec 000000c0 c037e328
> [ 0.646663] df00: e080df40 c037e328 c21fd600 00000000 c12e093d c13d5ebc 00000000 244cee50
> [ 0.646929] df20: 244cee50 c1655918 c1655aa0 c21f9300 deffff00 c13578a8 00000000 00000000
> [ 0.647197] df40: e080df68 c1501898 00000007 00000007 00000000 c1501900 00000019 c21f9300
> [ 0.647462] df60: 00000007 00000000 e080df88 c15017c0 c2143a00 c215c200 00000000 00000000
> [ 0.647736] df80: 00000000 00000000 e080df98 c150163c 00000000 c0f6fa60 e080dfa8 c0f6fa80
> [ 0.648006] dfa0: 00000000 00000000 00000000 c030016c 00000000 00000000 00000000 00000000
> [ 0.648273] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.648536] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
> [ 0.648801] Call trace:
> [ 0.648840] __fortify_panic from add_sysfs_param+0x224/0x228
> [ 0.649129] add_sysfs_param from kernel_add_sysfs_param+0x5c/0xa0
> [ 0.649348] kernel_add_sysfs_param from param_sysfs_builtin+0xf4/0x130
> [ 0.649572] param_sysfs_builtin from param_sysfs_builtin_init+0x30/0x38
> [ 0.649801] param_sysfs_builtin_init from do_one_initcall+0xd0/0x2d4
> [ 0.650021] do_one_initcall from do_initcall_level+0x9c/0x104
> [ 0.650223] do_initcall_level from do_initcalls+0x74/0xb0
> [ 0.650412] do_initcalls from kernel_init_freeable+0x10c/0x158
> [ 0.650612] kernel_init_freeable from kernel_init+0x20/0x1cc
> [ 0.650810] kernel_init from ret_from_fork+0x14/0x28
> [ 0.650984] Exception stack(0xe080dfb0 to 0xe080dff8)
> [ 0.651164] dfa0: 00000000 00000000 00000000 00000000
> [ 0.651427] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.651697] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 0.652032] Code: e8bd4bf0 eae457a7 e92d4800 ebe4aaef (e7f001f2)
> [ 0.652584] ---[ end trace 0000000000000000 ]---
> [ 0.652825] note: swapper/0[1] exited with irqs disabled
> [ 0.653314] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> [ 0.654033] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
>
> I haven't had a chance to really look over this too much but I figured I
> would get the report out sooner rather than later, especially with the
> merge window being around the corner. If there is any other information
> I can provide or patches I can test, I am more than happy to do so.
>
> Cheers,
> Nathan
>
> # bad: [57f962b956f1d116cd64d5c406776c4975de549d] Add linux-next specific files for 20240912
> # good: [77f587896757708780a7e8792efe62939f25a5ab] Merge tag 'arm-fixes-6.11-3' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc
> git bisect start '57f962b956f1d116cd64d5c406776c4975de549d' '77f587896757708780a7e8792efe62939f25a5ab'
> # good: [5e6a31306949eb18be8d6dc7ad6c42f8bea8e743] Merge branch 'main' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
> git bisect good 5e6a31306949eb18be8d6dc7ad6c42f8bea8e743
> # bad: [9802faa85f4ccbc8cc0893fe76b939a9c56b9e62] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-power-supply.git
> git bisect bad 9802faa85f4ccbc8cc0893fe76b939a9c56b9e62
> # good: [793a135214a81488066fb8ccecbd4f182c416326] drm/xe/mmio: Drop compatibility macros
> git bisect good 793a135214a81488066fb8ccecbd4f182c416326
> # good: [d8bfeb4282b1c55342d2dd946eaf00f4f13785db] Merge branch 'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394.git
> git bisect good d8bfeb4282b1c55342d2dd946eaf00f4f13785db
> # bad: [f5315deb662e813be5fa93f2b67d46fe9fcd383c] Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git
> git bisect bad f5315deb662e813be5fa93f2b67d46fe9fcd383c
> # good: [4b1d9019b26fd654ebc2d0d2e100ed56ef1821f0] ASoC: dt-bindings: amlogic,axg-sound-card: document clocks property
> git bisect good 4b1d9019b26fd654ebc2d0d2e100ed56ef1821f0
> # bad: [2ca98b409c36e91bb359a2997f4a7810e799bd62] Merge branch 'modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git
> git bisect bad 2ca98b409c36e91bb359a2997f4a7810e799bd62
> # good: [d39b510a145a4766906cd49177695913d6e6bfd2] Add audio support for the MediaTek Genio 350-evk
> git bisect good d39b510a145a4766906cd49177695913d6e6bfd2
> # good: [43fbb2c702663d7af844ee952aec224a0e059e26] ASoC: loongson: Simplify code formatting
> git bisect good 43fbb2c702663d7af844ee952aec224a0e059e26
> # good: [0b0aa67baa8904e3c1e13be48a2ca125f59ead3d] ASoC: amd: acp: remove MODULE_ALIAS for sof based generic machine driver
> git bisect good 0b0aa67baa8904e3c1e13be48a2ca125f59ead3d
> # good: [8905d39085c60a13d47bd07d2766bfdde933cc8d] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git
> git bisect good 8905d39085c60a13d47bd07d2766bfdde933cc8d
> # good: [907fa79d787f6f762c0afb67b8b02be8ed1f7bd2] MAINTAINERS: scale modules with more reviewers
> git bisect good 907fa79d787f6f762c0afb67b8b02be8ed1f7bd2
> # bad: [e1d90ff7bc4b93c0b6c4821bef71b51ce145d7a7] module: abort module loading when sysfs setup suffer errors
> git bisect bad e1d90ff7bc4b93c0b6c4821bef71b51ce145d7a7
> # bad: [7125cb974977aa80959817548b5221314fe46bc0] params: Annotate struct module_param_attrs with __counted_by()
> git bisect bad 7125cb974977aa80959817548b5221314fe46bc0
> # first bad commit: [7125cb974977aa80959817548b5221314fe46bc0] params: Annotate struct module_param_attrs with __counted_by()
Thanks for reporting this.
Changing
memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0]));
to
memset(mk->mp->attrs + mk->mp->num - 1, 0, sizeof(mk->mp->attrs[0]));
fixes the false-positive warning
memset: detected buffer overflow: 32 byte write of buffer size 0
even though the pointers have the same value. Does anyone know why?
Thanks,
Thorsten
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