Allow read only mounts for filesystems that do not have maximum timestamps beyond the y2038 expiry timestamp.
Also, allow a sysctl override to all such filesystems to be mounted with write permissions. A boot param supports initial override of these checks from the early boot without recompilation.
Suggested-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Deepa Dinamani deepa.kernel@gmail.com --- fs/inode.c | 15 +++++++++++++++ fs/internal.h | 2 ++ fs/namespace.c | 12 ++++++++++++ fs/super.c | 7 +++++++ include/linux/fs.h | 1 + include/linux/time64.h | 4 ++++ include/uapi/linux/fs.h | 6 +++++- kernel/sysctl.c | 7 +++++++ 8 files changed, 53 insertions(+), 1 deletion(-)
diff --git a/fs/inode.c b/fs/inode.c index 0b3ee89..7967f9c 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -75,6 +75,21 @@ static DEFINE_PER_CPU(unsigned long, nr_unused);
static struct kmem_cache *inode_cachep __read_mostly;
+struct vfs_max_timestamp_check timestamp_check = { + .timestamp_supported = Y2038_EXPIRY_TIMESTAMP, + .check_on = 0, +}; + +static int __init setup_timestamp_check(char *str) +{ + if (*str) + return 0; + timestamp_check.check_on = 1; + return 1; +} + +__setup("fstimestampcheck", setup_timestamp_check); + static long get_nr_inodes(void) { int i; diff --git a/fs/internal.h b/fs/internal.h index 11c6d89..4b3cb9e 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -67,6 +67,8 @@ extern int finish_automount(struct vfsmount *, struct path *);
extern int sb_prepare_remount_readonly(struct super_block *);
+extern bool sb_file_times_updatable(struct super_block *sb); + extern void __init mnt_init(void);
extern int __mnt_want_write(struct vfsmount *); diff --git a/fs/namespace.c b/fs/namespace.c index 8bfad42..dbf3f1c 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -538,6 +538,18 @@ static void __mnt_unmake_readonly(struct mount *mnt) unlock_mount_hash(); }
+bool sb_file_times_updatable(struct super_block *sb) +{ + + if (!timestamp_check.check_on) + return true; + + if (sb->s_time_max > timestamp_check.timestamp_supported) + return true; + + return false; +} + int sb_prepare_remount_readonly(struct super_block *sb) { struct mount *mnt; diff --git a/fs/super.c b/fs/super.c index f9c2241..4e7577b 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1245,6 +1245,13 @@ mount_fs(struct file_system_type *type, int flags, const char *name, void *data) WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to " "negative value (%lld)\n", type->name, sb->s_maxbytes);
+ if (!(sb->s_flags & MS_RDONLY) && !sb_file_times_updatable(sb)) { + WARN(1, "File times cannot be updated on the filesystem.\n"); + WARN(1, "Retry mounting the filesystem readonly.\n"); + error = -EROFS; + goto out_sb; + } + up_write(&sb->s_umount); free_secdata(secdata); return root; diff --git a/include/linux/fs.h b/include/linux/fs.h index ef55dfb..e12a32d 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -68,6 +68,7 @@ extern struct inodes_stat_t inodes_stat; extern int leases_enable, lease_break_time; extern int sysctl_protected_symlinks; extern int sysctl_protected_hardlinks; +extern struct vfs_max_timestamp_check timestamp_check;
struct buffer_head; typedef int (get_block_t)(struct inode *inode, sector_t iblock, diff --git a/include/linux/time64.h b/include/linux/time64.h index 25433b18..906e0b3 100644 --- a/include/linux/time64.h +++ b/include/linux/time64.h @@ -43,6 +43,10 @@ struct itimerspec64 { #define KTIME_MAX ((s64)~((u64)1 << 63)) #define KTIME_SEC_MAX (KTIME_MAX / NSEC_PER_SEC)
+/* Timestamps on boundary */ +#define Y2038_EXPIRY_TIMESTAMP S32_MAX /* 2147483647 */ +#define Y2106_EXPIRY_TIMESTAMP U32_MAX /* 4294967295 */ + #if __BITS_PER_LONG == 64
static inline struct timespec timespec64_to_timespec(const struct timespec64 ts64) diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 048a85e..125e4ae 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -91,6 +91,11 @@ struct files_stat_struct { unsigned long max_files; /* tunable */ };
+struct vfs_max_timestamp_check { + time64_t timestamp_supported; + int check_on; +}; + struct inodes_stat_t { long nr_inodes; long nr_unused; @@ -100,7 +105,6 @@ struct inodes_stat_t {
#define NR_FILE 8192 /* this can well be larger on a larger system */
- /* * These are the fs-independent mount-flags: up to 32 flags are supported */ diff --git a/kernel/sysctl.c b/kernel/sysctl.c index bb260ce..eda60d9 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1667,6 +1667,13 @@ static struct ctl_table fs_table[] = { .proc_handler = proc_doulongvec_minmax, }, { + .procname = "fs-timestamp-check-on", + .data = ×tamp_check.check_on, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec, + }, + { .procname = "nr_open", .data = &sysctl_nr_open, .maxlen = sizeof(unsigned int),