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-rw-r--r--Documentation/admin-guide/xfs.rst1
-rw-r--r--fs/xfs/Kconfig27
-rw-r--r--fs/xfs/xfs_super.c13
3 files changed, 41 insertions, 0 deletions
diff --git a/Documentation/admin-guide/xfs.rst b/Documentation/admin-guide/xfs.rst
index e2561416391c..e85a9404d5c0 100644
--- a/Documentation/admin-guide/xfs.rst
+++ b/Documentation/admin-guide/xfs.rst
@@ -240,6 +240,7 @@ Deprecated Mount Options
Name Removal Schedule
=========================== ================
Mounting with V4 filesystem September 2030
+Mounting ascii-ci filesystem September 2030
ikeep/noikeep September 2025
attr2/noattr2 September 2025
=========================== ================
diff --git a/fs/xfs/Kconfig b/fs/xfs/Kconfig
index 05bc865142b8..52e1823241fb 100644
--- a/fs/xfs/Kconfig
+++ b/fs/xfs/Kconfig
@@ -47,6 +47,33 @@ config XFS_SUPPORT_V4
To continue supporting the old V4 format (crc=0), say Y.
To close off an attack surface, say N.
+config XFS_SUPPORT_ASCII_CI
+ bool "Support deprecated case-insensitive ascii (ascii-ci=1) format"
+ depends on XFS_FS
+ default y
+ help
+ The ASCII case insensitivity filesystem feature only works correctly
+ on systems that have been coerced into using ISO 8859-1, and it does
+ not work on extended attributes. The kernel has no visibility into
+ the locale settings in userspace, so it corrupts UTF-8 names.
+ Enabling this feature makes XFS vulnerable to mixed case sensitivity
+ attacks. Because of this, the feature is deprecated. All users
+ should upgrade by backing up their files, reformatting, and restoring
+ from the backup.
+
+ Administrators and users can detect such a filesystem by running
+ xfs_info against a filesystem mountpoint and checking for a string
+ beginning with "ascii-ci=". If the string "ascii-ci=1" is found, the
+ filesystem is a case-insensitive filesystem. If no such string is
+ found, please upgrade xfsprogs to the latest version and try again.
+
+ This option will become default N in September 2025. Support for the
+ feature will be removed entirely in September 2030. Distributors
+ can say N here to withdraw support earlier.
+
+ To continue supporting case-insensitivity (ascii-ci=1), say Y.
+ To close off an attack surface, say N.
+
config XFS_QUOTA
bool "XFS Quota support"
depends on XFS_FS
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 4f814f9e12ab..4d2e87462ac4 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1548,6 +1548,19 @@ xfs_fs_fill_super(
#endif
}
+ /* ASCII case insensitivity is undergoing deprecation. */
+ if (xfs_has_asciici(mp)) {
+#ifdef CONFIG_XFS_SUPPORT_ASCII_CI
+ xfs_warn_once(mp,
+ "Deprecated ASCII case-insensitivity feature (ascii-ci=1) will not be supported after September 2030.");
+#else
+ xfs_warn(mp,
+ "Deprecated ASCII case-insensitivity feature (ascii-ci=1) not supported by kernel.");
+ error = -EINVAL;
+ goto out_free_sb;
+#endif
+ }
+
/* Filesystem claims it needs repair, so refuse the mount. */
if (xfs_has_needsrepair(mp)) {
xfs_warn(mp, "Filesystem needs repair. Please run xfs_repair.");