On Thu, Oct 31, 2024 at 02:31:21PM -0300, André Almeida wrote: > 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 <andrealmeid@xxxxxxxxxx> > > > Reviewed-by: Gabriel Krisman Bertazi <krisman@xxxxxxx> > > > --- > > > 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(). Upon a quick glance, it looks like all of the btrfs sysfs functions properly match the ->show() and ->store() type in kobj_attribute, so there is no type mismatch when they are called indirectly. Cheers, Nathan