From 49a0a0f0ab38d8f006f9c9fb64e4a7da888a37f4 Mon Sep 17 00:00:00 2001 From: Vasant Karasulli Date: Thu, 17 Mar 2022 10:50:47 +0100 Subject: [PATCH] exfat: allow access to paths with trailing dots The Linux kernel exfat driver currently unconditionally strips trailing periods '.' from path components. This isdone intentionally, loosely following Windows behaviour and specifications which state: #exFAT The concatenated file name has the same set of illegal characters as other FAT-based file systems (see Table 31). #FAT ... Leading and trailing spaces in a long name are ignored. Leading and embedded periods are allowed in a name and are stored in the long name. Trailing periods are ignored. Note: Leading and trailing space ' ' characters are currently retained by Linux kernel exfat, in conflict with the above specification. On Windows 10, trailing and leading space ' ' characters are stripped from the filenames. Some implementations, such as fuse-exfat, don't perform path trailer removal. When mounting images which contain trailing-dot paths, these paths are unreachable, e.g.: + mount.exfat-fuse /dev/zram0 /mnt/test/ FUSE exfat 1.3.0 + cd /mnt/test/ + touch fuse_created_dots... ' fuse_created_spaces ' + ls -l total 0 -rwxrwxrwx 1 root 0 0 Aug 18 09:45 ' fuse_created_spaces ' -rwxrwxrwx 1 root 0 0 Aug 18 09:45 fuse_created_dots... + cd / + umount /mnt/test/ + mount -t exfat /dev/zram0 /mnt/test + cd /mnt/test + ls -l ls: cannot access 'fuse_created_dots...': No such file or directory total 0 -rwxr-xr-x 1 root 0 0 Aug 18 09:45 ' fuse_created_spaces ' -????????? ? ? ? ? ? fuse_created_dots... + touch kexfat_created_dots... ' kexfat_created_spaces ' + ls -l ls: cannot access 'fuse_created_dots...': No such file or directory total 0 -rwxr-xr-x 1 root 0 0 Aug 18 09:45 ' fuse_created_spaces ' -rwxr-xr-x 1 root 0 0 Aug 18 09:45 ' kexfat_created_spaces ' -????????? ? ? ? ? ? fuse_created_dots... -rwxr-xr-x 1 root 0 0 Aug 18 09:45 kexfat_created_dots + cd / + umount /mnt/test/ This commit adds "keep_last_dots" mount option that controls whether or not trailing periods '.' are stripped from path components during file lookup or file creation. This mount option can be used to access paths with trailing periods and disallow creating files with names with trailing periods. E.g. continuing from the previous example: + mount -t exfat -o keep_last_dots /dev/zram0 /mnt/test + cd /mnt/test + ls -l total 0 -rwxr-xr-x 1 root 0 0 Aug 18 10:32 ' fuse_created_spaces ' -rwxr-xr-x 1 root 0 0 Aug 18 10:32 ' kexfat_created_spaces ' -rwxr-xr-x 1 root 0 0 Aug 18 10:32 fuse_created_dots... -rwxr-xr-x 1 root 0 0 Aug 18 10:32 kexfat_created_dots + echo > kexfat_created_dots_again... sh: kexfat_created_dots_again...: Invalid argument Link: https://bugzilla.suse.com/show_bug.cgi?id=1188964 Link: https://lore.kernel.org/linux-fsdevel/003b01d755e4$31fb0d80$95f12880$ @samsung.com/ Link: https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification Suggested-by: Takashi Iwai Signed-off-by: Vasant Karasulli Co-developed-by: David Disseldorp Signed-off-by: David Disseldorp Signed-off-by: Namjae Jeon --- fs/exfat/exfat_fs.h | 3 ++- fs/exfat/namei.c | 50 ++++++++++++++++++++++++++++++++------------- fs/exfat/super.c | 7 +++++++ 3 files changed, 45 insertions(+), 15 deletions(-) diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h index 619e5b4bed100..c6800b8809203 100644 --- a/fs/exfat/exfat_fs.h +++ b/fs/exfat/exfat_fs.h @@ -203,7 +203,8 @@ struct exfat_mount_options { /* on error: continue, panic, remount-ro */ enum exfat_error_mode errors; unsigned utf8:1, /* Use of UTF-8 character set */ - discard:1; /* Issue discard requests on deletions */ + discard:1, /* Issue discard requests on deletions */ + keep_last_dots:1; /* Keep trailing periods in paths */ int time_offset; /* Offset of timestamps from UTC (in minutes) */ }; diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c index af4eb39cc0c3c..a4f8010fbd38e 100644 --- a/fs/exfat/namei.c +++ b/fs/exfat/namei.c @@ -65,11 +65,14 @@ static int exfat_d_revalidate(struct dentry *dentry, unsigned int flags) return ret; } -/* returns the length of a struct qstr, ignoring trailing dots */ -static unsigned int exfat_striptail_len(unsigned int len, const char *name) +/* returns the length of a struct qstr, ignoring trailing dots if necessary */ +static unsigned int exfat_striptail_len(unsigned int len, const char *name, + bool keep_last_dots) { - while (len && name[len - 1] == '.') - len--; + if (!keep_last_dots) { + while (len && name[len - 1] == '.') + len--; + } return len; } @@ -83,7 +86,8 @@ static int exfat_d_hash(const struct dentry *dentry, struct qstr *qstr) struct super_block *sb = dentry->d_sb; struct nls_table *t = EXFAT_SB(sb)->nls_io; const unsigned char *name = qstr->name; - unsigned int len = exfat_striptail_len(qstr->len, qstr->name); + unsigned int len = exfat_striptail_len(qstr->len, qstr->name, + EXFAT_SB(sb)->options.keep_last_dots); unsigned long hash = init_name_hash(dentry); int i, charlen; wchar_t c; @@ -104,8 +108,10 @@ static int exfat_d_cmp(const struct dentry *dentry, unsigned int len, { struct super_block *sb = dentry->d_sb; struct nls_table *t = EXFAT_SB(sb)->nls_io; - unsigned int alen = exfat_striptail_len(name->len, name->name); - unsigned int blen = exfat_striptail_len(len, str); + unsigned int alen = exfat_striptail_len(name->len, name->name, + EXFAT_SB(sb)->options.keep_last_dots); + unsigned int blen = exfat_striptail_len(len, str, + EXFAT_SB(sb)->options.keep_last_dots); wchar_t c1, c2; int charlen, i; @@ -136,7 +142,8 @@ static int exfat_utf8_d_hash(const struct dentry *dentry, struct qstr *qstr) { struct super_block *sb = dentry->d_sb; const unsigned char *name = qstr->name; - unsigned int len = exfat_striptail_len(qstr->len, qstr->name); + unsigned int len = exfat_striptail_len(qstr->len, qstr->name, + EXFAT_SB(sb)->options.keep_last_dots); unsigned long hash = init_name_hash(dentry); int i, charlen; unicode_t u; @@ -161,8 +168,11 @@ static int exfat_utf8_d_cmp(const struct dentry *dentry, unsigned int len, const char *str, const struct qstr *name) { struct super_block *sb = dentry->d_sb; - unsigned int alen = exfat_striptail_len(name->len, name->name); - unsigned int blen = exfat_striptail_len(len, str); + unsigned int alen = exfat_striptail_len(name->len, name->name, + EXFAT_SB(sb)->options.keep_last_dots); + unsigned int blen = exfat_striptail_len(len, str, + EXFAT_SB(sb)->options.keep_last_dots); + unicode_t u_a, u_b; int charlen, i; @@ -416,13 +426,25 @@ static int __exfat_resolve_path(struct inode *inode, const unsigned char *path, struct super_block *sb = inode->i_sb; struct exfat_sb_info *sbi = EXFAT_SB(sb); struct exfat_inode_info *ei = EXFAT_I(inode); + int pathlen = strlen(path); - /* strip all trailing periods */ - namelen = exfat_striptail_len(strlen(path), path); + /* + * get the length of the pathname excluding + * trailing periods, if any. + */ + namelen = exfat_striptail_len(pathlen, path, false); + if (EXFAT_SB(sb)->options.keep_last_dots) { + /* + * Do not allow the creation of files with names + * ending with period(s). + */ + if (!lookup && (namelen < pathlen)) + return -EINVAL; + namelen = pathlen; + } if (!namelen) return -ENOENT; - - if (strlen(path) > (MAX_NAME_LENGTH * MAX_CHARSET_SIZE)) + if (pathlen > (MAX_NAME_LENGTH * MAX_CHARSET_SIZE)) return -ENAMETOOLONG; /* diff --git a/fs/exfat/super.c b/fs/exfat/super.c index 8c9fb7dcec16a..4c3f80ed17b1e 100644 --- a/fs/exfat/super.c +++ b/fs/exfat/super.c @@ -174,6 +174,8 @@ static int exfat_show_options(struct seq_file *m, struct dentry *root) seq_puts(m, ",errors=remount-ro"); if (opts->discard) seq_puts(m, ",discard"); + if (opts->keep_last_dots) + seq_puts(m, ",keep_last_dots"); if (opts->time_offset) seq_printf(m, ",time_offset=%d", opts->time_offset); return 0; @@ -217,6 +219,7 @@ enum { Opt_charset, Opt_errors, Opt_discard, + Opt_keep_last_dots, Opt_time_offset, /* Deprecated options */ @@ -243,6 +246,7 @@ static const struct fs_parameter_spec exfat_parameters[] = { fsparam_string("iocharset", Opt_charset), fsparam_enum("errors", Opt_errors, exfat_param_enums), fsparam_flag("discard", Opt_discard), + fsparam_flag("keep_last_dots", Opt_keep_last_dots), fsparam_s32("time_offset", Opt_time_offset), __fsparam(NULL, "utf8", Opt_utf8, fs_param_deprecated, NULL), @@ -297,6 +301,9 @@ static int exfat_parse_param(struct fs_context *fc, struct fs_parameter *param) case Opt_discard: opts->discard = 1; break; + case Opt_keep_last_dots: + opts->keep_last_dots = 1; + break; case Opt_time_offset: /* * Make the limit 24 just in case someone invents something -- 2.39.5