From nobody Fri Dec 19 17:56:15 2025 Received: from mail-oi1-f202.google.com (mail-oi1-f202.google.com [209.85.167.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 115811F8755 for ; Fri, 5 Dec 2025 00:58:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764896330; cv=none; b=A80muf9HNA9EHDP3Dds6jGvgDDDiVOqD4MsoHkJRjIAJmfZjYqg7PGyBVTRBywR6N4HeMSr/HJ0kymIQ5rhUlYt2BED6L82A9qHl+E8e7ZJ9vFLWRxDLmdR3FqKXX8pNlBk6n1fR/n7hItEVJYy+pvZjDM7I3kn/g+0morhzotM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764896330; c=relaxed/simple; bh=nyHWTFoGvASer3toat4ImRw6FmdnkyEWU7Xu2iHxdEk=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=UWVRCo6dGBjCVrYpRLke1o0c6eUylUul7fIQiEELIrpRCccix2UEdHf0dXGh++13Rlh3Qi8sMTSr9OPgCNiTihqqP+lBcx7l7bjOZabUZ0JjbqL1aSCw6xiTWn2lqmUPTtOiNd/FCMOciIltnSEyFz77n5Jxxkk2rWj0bWSrhDs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--avagin.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=eNZEsLmA; arc=none smtp.client-ip=209.85.167.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--avagin.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="eNZEsLmA" Received: by mail-oi1-f202.google.com with SMTP id 5614622812f47-4537c9e1c14so1267410b6e.1 for ; Thu, 04 Dec 2025 16:58:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1764896327; x=1765501127; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=l1Ka/G7ByT2+kY8UIiF65zUCvkc5PFIL+KWxYDYgrVo=; b=eNZEsLmAdpb0BU2UpV5lhEny7gj5K5inc2LLvEIbLCq3aW6Wl8RuKrlK16q0FbPdDY cF6VTXRH+Q2yFbiCH9jUTQKHpfaBFNUtzYrqjcBu3fD1Z8i1NXxLk+wf7QQKQ9BnrzJi 6YZLicRaWzMU/MzBBy8odRJR3jPUSd2nji/PacrYeaakDSDUxvWjY5fy0f6kRD0B6NrC jwzMeD6E+1UtawogGpdAQZr7Ir30WRkNlJhKprd8DX81gWIp4QZ8GWO1r4f9z0xjEVv2 ivmF3q7sQrG1YRJfijmK2DKI37V8MC9j5HLM5zx4RzNntOlvx8vJFy+nrKkStaqeZeXp vXsg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764896327; x=1765501127; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=l1Ka/G7ByT2+kY8UIiF65zUCvkc5PFIL+KWxYDYgrVo=; b=p2P8w9TzDdvWYIPp8qeVqPWus9HZtaLIxqciGRMdwNzuKpP82ibBHdaMTjCtoB1Kvv 9L51D3nmJp8abBMDTeSLoTdOHGF9YkwuV1dewKlZXhRKqvVHznKwsE8Qa7NXVVuCIMzC eEJhweEDXV/0ZKteh2hpf5DxSHCI2iBN3w8MkRopsO2HMmXyVr3oj8Pwpta+cbukuimU Jat91e3W9YS8+Jm3zUN5ewNGtmuPHBdCaBfywNIfOaRHS8dz4mT+CKc50JAtca7h4hjz VAvQYfalG1fNOKZQ+7hDmHlEQjMFX8lUrUUyXnmK0w/F91m3wqoyZhM2nCn87BvTBtBT erpg== X-Gm-Message-State: AOJu0YxfFsZRDwr6k1M0ItR4sblc9WO8qAMckMTn8aQEdJbba0zXdH12 3QsLUco0r7vOYl8B4OoIFYRzq1OBzPzVQqdMlCEch6DpkgQozmbCZ1Pc6tlvQNJOvGr08WoXGJv s+/X2vA== X-Google-Smtp-Source: AGHT+IGmtosd8xmps/oV4TZgOUFGtK1BT8mv/MmkumMBnl/inyl5u1+B5QcUb//XVfD1YOf+RZc7lMo25M0= X-Received: from iobgp24.prod.google.com ([2002:a05:6602:e18:b0:949:60d:4912]) (user=avagin job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6808:1185:b0:44f:e61d:189f with SMTP id 5614622812f47-4536e3dcc04mr4462771b6e.13.1764896327255; Thu, 04 Dec 2025 16:58:47 -0800 (PST) Date: Fri, 5 Dec 2025 00:58:30 +0000 In-Reply-To: <20251205005841.3942668-1-avagin@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251205005841.3942668-1-avagin@google.com> X-Mailer: git-send-email 2.52.0.223.gf5cc29aaa4-goog Message-ID: <20251205005841.3942668-3-avagin@google.com> Subject: [PATCH 1/3] cgroup, binfmt_elf: Add hwcap masks to the misc controller From: Andrei Vagin To: Kees Cook Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, criu@lists.linux.dev, Tejun Heo , Johannes Weiner , "=?UTF-8?q?Michal=20Koutn=C3=BD?=" , Vipin Sharma , Jonathan Corbet , Andrei Vagin Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add an interface to the misc cgroup controller that allows masking out hardware capabilities (AT_HWCAP) reported to user-space processes. This provides a mechanism to restrict the features a containerized application can see. The new "misc.mask" cgroup file allows users to specify masks for AT_HWCAP, AT_HWCAP2, AT_HWCAP3, and AT_HWCAP4. The output of "misc.mask" is extended to display the effective mask, which is a combination of the masks from the current cgroup and all its ancestors. Signed-off-by: Andrei Vagin --- fs/binfmt_elf.c | 24 +++++-- include/linux/misc_cgroup.h | 25 +++++++ kernel/cgroup/misc.c | 126 ++++++++++++++++++++++++++++++++++++ 3 files changed, 171 insertions(+), 4 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 3eb734c192e9..59137784e81d 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -47,6 +47,7 @@ #include #include #include +#include #include #include =20 @@ -182,6 +183,21 @@ create_elf_tables(struct linux_binprm *bprm, const str= uct elfhdr *exec, int ei_index; const struct cred *cred =3D current_cred(); struct vm_area_struct *vma; + struct misc_cg *misc_cg; + u64 hwcap_mask[4] =3D {0, 0, 0, 0}; + + misc_cg =3D get_current_misc_cg(); + misc_cg_get_mask(MISC_CG_MASK_HWCAP, misc_cg, &hwcap_mask[0]); +#ifdef ELF_HWCAP2 + misc_cg_get_mask(MISC_CG_MASK_HWCAP2, misc_cg, &hwcap_mask[1]); +#endif +#ifdef ELF_HWCAP3 + misc_cg_get_mask(MISC_CG_MASK_HWCAP3, misc_cg, &hwcap_mask[2]); +#endif +#ifdef ELF_HWCAP4 + misc_cg_get_mask(MISC_CG_MASK_HWCAP4, misc_cg, &hwcap_mask[3]); +#endif + put_misc_cg(misc_cg); =20 /* * In some cases (e.g. Hyper-Threading), we want to avoid L1 @@ -246,7 +262,7 @@ create_elf_tables(struct linux_binprm *bprm, const stru= ct elfhdr *exec, */ ARCH_DLINFO; #endif - NEW_AUX_ENT(AT_HWCAP, ELF_HWCAP); + NEW_AUX_ENT(AT_HWCAP, ELF_HWCAP & ~hwcap_mask[0]); NEW_AUX_ENT(AT_PAGESZ, ELF_EXEC_PAGESIZE); NEW_AUX_ENT(AT_CLKTCK, CLOCKS_PER_SEC); NEW_AUX_ENT(AT_PHDR, phdr_addr); @@ -264,13 +280,13 @@ create_elf_tables(struct linux_binprm *bprm, const st= ruct elfhdr *exec, NEW_AUX_ENT(AT_SECURE, bprm->secureexec); NEW_AUX_ENT(AT_RANDOM, (elf_addr_t)(unsigned long)u_rand_bytes); #ifdef ELF_HWCAP2 - NEW_AUX_ENT(AT_HWCAP2, ELF_HWCAP2); + NEW_AUX_ENT(AT_HWCAP2, ELF_HWCAP2 & ~hwcap_mask[1]); #endif #ifdef ELF_HWCAP3 - NEW_AUX_ENT(AT_HWCAP3, ELF_HWCAP3); + NEW_AUX_ENT(AT_HWCAP3, ELF_HWCAP3 & ~hwcap_mask[2]); #endif #ifdef ELF_HWCAP4 - NEW_AUX_ENT(AT_HWCAP4, ELF_HWCAP4); + NEW_AUX_ENT(AT_HWCAP4, ELF_HWCAP4 & ~hwcap_mask[3]); #endif NEW_AUX_ENT(AT_EXECFN, bprm->exec); if (k_platform) { diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h index 0cb36a3ffc47..cff830c238fb 100644 --- a/include/linux/misc_cgroup.h +++ b/include/linux/misc_cgroup.h @@ -8,6 +8,8 @@ #ifndef _MISC_CGROUP_H_ #define _MISC_CGROUP_H_ =20 +#include + /** * enum misc_res_type - Types of misc cgroup entries supported by the host. */ @@ -26,6 +28,20 @@ enum misc_res_type { MISC_CG_RES_TYPES }; =20 +enum misc_mask_type { + MISC_CG_MASK_HWCAP, +#ifdef ELF_HWCAP2 + MISC_CG_MASK_HWCAP2, +#endif +#ifdef ELF_HWCAP3 + MISC_CG_MASK_HWCAP3, +#endif +#ifdef ELF_HWCAP4 + MISC_CG_MASK_HWCAP4, +#endif + MISC_CG_MASK_TYPES +}; + struct misc_cg; =20 #ifdef CONFIG_CGROUP_MISC @@ -62,12 +78,15 @@ struct misc_cg { struct cgroup_file events_local_file; =20 struct misc_res res[MISC_CG_RES_TYPES]; + u64 mask[MISC_CG_MASK_TYPES]; }; =20 int misc_cg_set_capacity(enum misc_res_type type, u64 capacity); int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg, u64 am= ount); void misc_cg_uncharge(enum misc_res_type type, struct misc_cg *cg, u64 amo= unt); =20 +int misc_cg_get_mask(enum misc_mask_type type, struct misc_cg *cg, u64 *pm= ask); + /** * css_misc() - Get misc cgroup from the css. * @css: cgroup subsys state object. @@ -134,5 +153,11 @@ static inline void put_misc_cg(struct misc_cg *cg) { } =20 +static inline int misc_cg_get_mask(enum misc_mask_type type, struct misc_c= g *cg, u64 *pmask) +{ + *pmask =3D 0; + return 0; +} + #endif /* CONFIG_CGROUP_MISC */ #endif /* _MISC_CGROUP_H_ */ diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c index 6a01d91ea4cb..d1386d86060f 100644 --- a/kernel/cgroup/misc.c +++ b/kernel/cgroup/misc.c @@ -30,6 +30,19 @@ static const char *const misc_res_name[] =3D { #endif }; =20 +static const char *const misc_mask_name[] =3D { + "AT_HWCAP", +#ifdef ELF_HWCAP2 + "AT_HWCAP2", +#endif +#ifdef ELF_HWCAP3 + "AT_HWCAP3", +#endif +#ifdef ELF_HWCAP4 + "AT_HWCAP4", +#endif +}; + /* Root misc cgroup */ static struct misc_cg root_cg; =20 @@ -71,6 +84,11 @@ static inline bool valid_type(enum misc_res_type type) return type >=3D 0 && type < MISC_CG_RES_TYPES; } =20 +static inline bool valid_mask_type(enum misc_mask_type type) +{ + return type >=3D 0 && type < MISC_CG_MASK_TYPES; +} + /** * misc_cg_set_capacity() - Set the capacity of the misc cgroup res. * @type: Type of the misc res. @@ -391,6 +409,109 @@ static int misc_events_local_show(struct seq_file *sf= , void *v) return __misc_events_show(sf, true); } =20 +/** + * misc_cg_get_mask() - Get the mask of the specified type. + * @type: The misc mask type. + * @cg: The misc cgroup. + * @pmask: Pointer to the resulting mask. + * + * This function calculates the effective mask for a given cgroup by walki= ng up + * the hierarchy and ORing the masks from all parent cgroupfs. The final r= esult + * is stored in the location pointed to by @pmask. + * + * Context: Any context. + * Return: 0 on success, -EINVAL if @type is invalid. + */ +int misc_cg_get_mask(enum misc_mask_type type, struct misc_cg *cg, u64 *pm= ask) +{ + struct misc_cg *i; + u64 mask =3D 0; + + if (!(valid_mask_type(type))) + return -EINVAL; + + for (i =3D cg; i; i =3D parent_misc(i)) + mask |=3D READ_ONCE(i->mask[type]); + + *pmask =3D mask; + return 0; +} + +/** + * misc_cg_mask_show() - Show the misc cgroup masks. + * @sf: Interface file + * @v: Arguments passed + * + * Context: Any context. + * Return: 0 to denote successful print. + */ +static int misc_cg_mask_show(struct seq_file *sf, void *v) +{ + struct misc_cg *cg =3D css_misc(seq_css(sf)); + int i; + + for (i =3D 0; i < MISC_CG_MASK_TYPES; i++) { + u64 rval, val =3D READ_ONCE(cg->mask[i]); + + misc_cg_get_mask(i, cg, &rval); + seq_printf(sf, "%s\t%#016llx\t%#016llx\n", misc_mask_name[i], val, rval); + } + + return 0; +} + +/** + * misc_cg_mask_write() - Update the mask of the specified type. + * @of: Handler for the file. + * @buf: The buffer containing the user's input. + * @nbytes: The number of bytes in @buf. + * @off: The offset in the file. + * + * This function parses a user-provided string to update a mask. + * The expected format is " ", for example: + * + * echo "AT_HWCAP 0xf00" > misc.mask + * + * Context: Process context. + * Return: The number of bytes processed on success, or a negative error c= ode + * on failure. + */ +static ssize_t misc_cg_mask_write(struct kernfs_open_file *of, char *buf, + size_t nbytes, loff_t off) +{ + struct misc_cg *cg; + u64 max; + int ret =3D 0, i; + enum misc_mask_type type =3D MISC_CG_MASK_TYPES; + char *token; + + buf =3D strstrip(buf); + token =3D strsep(&buf, " "); + + if (!token || !buf) + return -EINVAL; + + for (i =3D 0; i < MISC_CG_MASK_TYPES; i++) { + if (!strcmp(misc_mask_name[i], token)) { + type =3D i; + break; + } + } + + if (type =3D=3D MISC_CG_MASK_TYPES) + return -EINVAL; + + ret =3D kstrtou64(buf, 0, &max); + if (ret) + return ret; + + cg =3D css_misc(of_css(of)); + + WRITE_ONCE(cg->mask[type], max); + + return nbytes; +} + /* Misc cgroup interface files */ static struct cftype misc_cg_files[] =3D { { @@ -424,6 +545,11 @@ static struct cftype misc_cg_files[] =3D { .file_offset =3D offsetof(struct misc_cg, events_local_file), .seq_show =3D misc_events_local_show, }, + { + .name =3D "mask", + .write =3D misc_cg_mask_write, + .seq_show =3D misc_cg_mask_show, + }, {} }; =20 --=20 2.52.0.223.gf5cc29aaa4-goog