From dc4edae7f41dceb236553b61cda0383895293c90 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 27 Apr 2026 10:26:03 +0200 Subject: fs: move SB_I_USERNS_VISIBLE to FS_USERNS_MOUNT_RESTRICTED Whether a filesystem's mounts need to undergo a visibility check in user namespaces is a static property of the filesystem type, not a runtime property of each superblock instance. Both proc and sysfs always set SB_I_USERNS_VISIBLE on their superblocks unconditionally (sysfs does so on first creation, and subsequent mounts reuse the same superblock). Move this flag from sb->s_iflags (SB_I_USERNS_VISIBLE) to file_system_type->fs_flags (FS_USERNS_MOUNT_RESTRICTED) so the intent is expressed at the filesystem type level where it belongs. All check sites are updated to test sb->s_type->fs_flags instead of sb->s_iflags. The SB_I_NOEXEC and SB_I_NODEV flags remain on the superblock as they are runtime properties set during fill_super. Link: https://patch.msgid.link/72887c5b6204dc3adf5a53104f0be6bd8bc4f6cd.1777278334.git.legion@kernel.org Reviewed-by: Aleksa Sarai Signed-off-by: Christian Brauner --- include/linux/fs.h | 1 + include/linux/fs/super_types.h | 1 - 2 files changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/fs.h b/include/linux/fs.h index c37bb3c7de8b..e7ff9f8b1485 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2281,6 +2281,7 @@ struct file_system_type { #define FS_MGTIME 64 /* FS uses multigrain timestamps */ #define FS_LBS 128 /* FS supports LBS */ #define FS_POWER_FREEZE 256 /* Always freeze on suspend/hibernate */ +#define FS_USERNS_MOUNT_RESTRICTED 512 /* Restrict mount in userns if not already visible */ #define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */ int (*init_fs_context)(struct fs_context *); const struct fs_parameter_spec *parameters; diff --git a/include/linux/fs/super_types.h b/include/linux/fs/super_types.h index 383050e7fdf5..182efbeb9520 100644 --- a/include/linux/fs/super_types.h +++ b/include/linux/fs/super_types.h @@ -326,7 +326,6 @@ struct super_block { #define SB_I_STABLE_WRITES 0x00000008 /* don't modify blks until WB is done */ /* sb->s_iflags to limit user namespace mounts */ -#define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */ #define SB_I_IMA_UNVERIFIABLE_SIGNATURE 0x00000020 #define SB_I_UNTRUSTED_MOUNTER 0x00000040 #define SB_I_EVM_HMAC_UNSUPPORTED 0x00000080 -- cgit v1.2.3