From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1C75B12BF24; Thu, 31 Oct 2024 17:31:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.60.130.6 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730395920; cv=none; b=I/UTdlVfFP4pyupQUmqceBBOxJ/Du8TwkDK6MQ3nADuVnhZJOmV1F5CQ0GjMxdnfhSv9YRXon8QG3Sr5TYmqdHr1D9mXh1s5I+Ls7nrxaBH3wVcS92dRsOYdNNOqMRhWZMn/DVYkfoz8uBGFTaAtzYd4uSarODXDFRJgLw+1NaU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730395920; c=relaxed/simple; bh=xGVT2nBFCDAbzlIh7Ah1fbzejAdzg17V5Cpg2c4tHcY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Q6Z51Im0hI5/Uot/c32BU8E2YfPQbMT1lj+QYoTKOOPYHA48TLfYTVows6FMgNVQRV9Q3rbU9aph1+XKpPcKPNMMBqMuoxyltiNpQt5+gDDFwI7vJobbNXVviMoQnRS3EibzgpboHqInD8h2mKatWDj0SJCXZzJKv/Vy/F9otLo= ARC-Authentication-Results:i=1; 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b=L4WjqTxBbEYzeWZS79F4oi3fLN DQRV8F4k3QheS9+mQuPSDjQLUMzjppXK0+Up04zWhnkgMJVX6X50RZvY8sSMbfoBxnVm9Dn8sUTHN ylnFebThg+uuZpPbkrTdyM6qWuhC9pYOXmgkPYPunDWWVPud1qVSMdgb/ImjMbqL0wQNOZQcDV2Fb RATS7IzlnaLXDvV2SKK+kcI9XqANr2Hzhuxb+Z0AHcvsRfGzOX5Up5jLv4bKLk60BNY0W9OzGzza8 eDwMlr74hgZ2QqrKX5hKhINDjJxZjp34aG4t7EuRjCHEfzXCQcYdh5vtY5HoCLcCPuMQgWQbbMy0A 636bhaNw==; Received: from [189.78.222.89] (helo=[192.168.15.100]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1t6Z18-0007Hm-Rc; Thu, 31 Oct 2024 18:31:31 +0100 Message-ID: Date: Thu, 31 Oct 2024 14:31:21 -0300 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 8/9] tmpfs: Expose filesystem features via sysfs To: Nathan Chancellor Cc: Gabriel Krisman Bertazi , Alexander Viro , Christian Brauner , Jan Kara , Theodore Ts'o , Andreas Dilger , Hugh Dickins , Andrew Morton , Jonathan Corbet , smcv@collabora.com, kernel-dev@igalia.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, Gabriel Krisman Bertazi , llvm@lists.linux.dev, linux-btrfs@vger.kernel.org, Chris Mason References: <20241021-tonyk-tmpfs-v8-0-f443d5814194@igalia.com> <20241021-tonyk-tmpfs-v8-8-f443d5814194@igalia.com> <20241031051822.GA2947788@thelio-3990X> Content-Language: en-US From: =?UTF-8?Q?Andr=C3=A9_Almeida?= In-Reply-To: <20241031051822.GA2947788@thelio-3990X> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Nathan, Em 31/10/2024 02:18, Nathan Chancellor escreveu: > Hi André, > > On Mon, Oct 21, 2024 at 01:37:24PM -0300, André Almeida wrote: >> Expose filesystem features through sysfs, so userspace can query if >> tmpfs support casefold. >> >> This follows the same setup as defined by ext4 and f2fs to expose >> casefold support to userspace. >> >> Signed-off-by: André Almeida >> Reviewed-by: Gabriel Krisman Bertazi >> --- >> mm/shmem.c | 37 +++++++++++++++++++++++++++++++++++++ >> 1 file changed, 37 insertions(+) >> >> diff --git a/mm/shmem.c b/mm/shmem.c >> index ea01628e443423d82d44277e085b867ab9bf4b28..0739143d1419c732359d3a3c3457c3acb90c5b22 100644 >> --- a/mm/shmem.c >> +++ b/mm/shmem.c >> @@ -5546,3 +5546,40 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping, >> return page; >> } >> EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp); >> + >> +#if defined(CONFIG_SYSFS) && defined(CONFIG_TMPFS) >> +#if IS_ENABLED(CONFIG_UNICODE) >> +static DEVICE_STRING_ATTR_RO(casefold, 0444, "supported"); >> +#endif >> + >> +static struct attribute *tmpfs_attributes[] = { >> +#if IS_ENABLED(CONFIG_UNICODE) >> + &dev_attr_casefold.attr.attr, >> +#endif >> + NULL >> +}; >> + >> +static const struct attribute_group tmpfs_attribute_group = { >> + .attrs = tmpfs_attributes, >> + .name = "features" >> +}; >> + >> +static struct kobject *tmpfs_kobj; >> + >> +static int __init tmpfs_sysfs_init(void) >> +{ >> + int ret; >> + >> + tmpfs_kobj = kobject_create_and_add("tmpfs", fs_kobj); >> + if (!tmpfs_kobj) >> + return -ENOMEM; >> + >> + ret = sysfs_create_group(tmpfs_kobj, &tmpfs_attribute_group); >> + if (ret) >> + kobject_put(tmpfs_kobj); >> + >> + return ret; >> +} >> + >> +fs_initcall(tmpfs_sysfs_init); >> +#endif /* CONFIG_SYSFS && CONFIG_TMPFS */ >> >> -- >> 2.47.0 >> > > This change as commit 5132f08bd332 ("tmpfs: Expose filesystem features > via sysfs") in -next introduces a kCFI violation when accessing > /sys/fs/tmpfs/features/casefold. An attribute group created with > sysfs_create_group() has ->sysfs_ops() set to kobj_sysfs_ops, which has > a ->show() value of kobj_attr_show(). When kobj_attr_show() goes to call > the attribute's ->show() value after container_of(), there will be a > type mismatch in the case of the casefold attr, as it was defined with a > ->show() value of device_show_string() but that does not match the type > of ->show() in 'struct kobj_attribute'. > > I can easily reproduce this with the following commands: > > $ printf 'CONFIG_%s=y\n' CFI_CLANG UNICODE >kernel/configs/repro.config > > $ make -skj"$(nproc)" ARCH=arm64 LLVM=1 mrproper virtconfig repro.config Image.gz > ... > > $ curl -LSs https://github.com/ClangBuiltLinux/boot-utils/releases/download/20230707-182910/arm64-rootfs.cpio.zst | zstd -d >rootfs.cpio > > $ qemu-system-aarch64 \ > -display none \ > -nodefaults \ > -cpu max,pauth-impdef=true \ > -machine virt,gic-version=max,virtualization=true \ > -append 'console=ttyAMA0 earlycon rdinit=/bin/sh' \ > -kernel arch/arm64/boot/Image.gz \ > -initrd rootfs.cpio \ > -m 512m \ > -serial mon:stdio > ... > # mount -t sysfs sys /sys > # cat /sys/fs/tmpfs/features/casefold > [ 70.558496] CFI failure at kobj_attr_show+0x2c/0x4c (target: device_show_string+0x0/0x38; expected type: 0xc527b809) > [ 70.560018] Internal error: Oops - CFI: 00000000f2008228 [#1] PREEMPT SMP > [ 70.560647] Modules linked in: > [ 70.561770] CPU: 0 UID: 0 PID: 46 Comm: cat Not tainted 6.12.0-rc4-00008-g5132f08bd332 #1 > [ 70.562429] Hardware name: linux,dummy-virt (DT) > [ 70.562897] pstate: 21402009 (nzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) > [ 70.563377] pc : kobj_attr_show+0x2c/0x4c > [ 70.563674] lr : sysfs_kf_seq_show+0xb4/0x130 > [ 70.563987] sp : ffff80008043bac0 > [ 70.564236] x29: ffff80008043bac0 x28: 000000007ffff001 x27: 0000000000000000 > [ 70.564877] x26: 0000000001000000 x25: 000000007ffff001 x24: 0000000000000001 > [ 70.565339] x23: fff000000238a000 x22: ffff9fa31a3996f8 x21: fff00000023fc000 > [ 70.565806] x20: fff000000201df80 x19: fff000000238b000 x18: 0000000000000000 > [ 70.566273] x17: 00000000c527b809 x16: 00000000df43c25c x15: fff000001fef8200 > [ 70.566727] x14: 0000000000000000 x13: fff00000022450f0 x12: 0000000000001000 > [ 70.567177] x11: fff00000023fc000 x10: 0000000000000000 x9 : ffff9fa31a18fac4 > [ 70.567682] x8 : ffff9fa319badde4 x7 : 0000000000000000 x6 : 000000000000003f > [ 70.568138] x5 : 0000000000000040 x4 : 0000000000000000 x3 : 0000000000000004 > [ 70.568585] x2 : fff00000023fc000 x1 : ffff9fa31a881f90 x0 : fff000000201df80 > [ 70.569169] Call trace: > [ 70.569389] kobj_attr_show+0x2c/0x4c > [ 70.569706] sysfs_kf_seq_show+0xb4/0x130 > [ 70.570020] kernfs_seq_show+0x44/0x54 > [ 70.570280] seq_read_iter+0x14c/0x4b0 > [ 70.570543] kernfs_fop_read_iter+0x60/0x198 > [ 70.570820] copy_splice_read+0x1f0/0x2f4 > [ 70.571092] splice_direct_to_actor+0xf4/0x2e0 > [ 70.571376] do_splice_direct+0x68/0xb8 > [ 70.571626] do_sendfile+0x1e8/0x488 > [ 70.571874] __arm64_sys_sendfile64+0xe0/0x12c > [ 70.572161] invoke_syscall+0x58/0x114 > [ 70.572424] el0_svc_common+0xa8/0xdc > [ 70.572676] do_el0_svc+0x1c/0x28 > [ 70.572910] el0_svc+0x38/0x68 > [ 70.573132] el0t_64_sync_handler+0x90/0xfc > [ 70.573394] el0t_64_sync+0x190/0x19 > [ 70.574001] Code: 72970131 72b8a4f1 6b11021f 54000040 (d4304500) > [ 70.574635] ---[ end trace 0000000000000000 ]--- > > I am not sure if there is a better API exists or if a local copy should > be rolled but I think the current scheme is definitely wrong because > there is no 'struct device' here. > Thank you for the report, I'm trying to fix it, it seems I have used something for device drivers in a filesystem. I wonder how btrfs doesn't get this error, since tmpfs_sysfs_init() is very similar to btrfs_init_sysfs(). > If there is any patch I can test or further information I can provide, I > am more than happy to do so. > > Cheers, > Nathan