4.17-stable review patch. If anyone has any objections, please let me know.
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From: OGAWA Hirofumi hirofumi@mail.parknet.co.jp
commit 35033ab988c396ad7bce3b6d24060c16a9066db8 upstream.
In parse_options(), if match_strdup() failed, parse_options() leaves opts->iocharset in unexpected state (i.e. still pointing the freed string). And this can be the cause of double free.
To fix, this initialize opts->iocharset always when freeing.
Link: http://lkml.kernel.org/r/8736wp9dzc.fsf@mail.parknet.co.jp Signed-off-by: OGAWA Hirofumi hirofumi@mail.parknet.co.jp Reported-by: syzbot+90b8e10515ae88228a92@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/fat/inode.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)
--- a/fs/fat/inode.c +++ b/fs/fat/inode.c @@ -697,13 +697,21 @@ static void fat_set_state(struct super_b brelse(bh); }
+static void fat_reset_iocharset(struct fat_mount_options *opts) +{ + if (opts->iocharset != fat_default_iocharset) { + /* Note: opts->iocharset can be NULL here */ + kfree(opts->iocharset); + opts->iocharset = fat_default_iocharset; + } +} + static void delayed_free(struct rcu_head *p) { struct msdos_sb_info *sbi = container_of(p, struct msdos_sb_info, rcu); unload_nls(sbi->nls_disk); unload_nls(sbi->nls_io); - if (sbi->options.iocharset != fat_default_iocharset) - kfree(sbi->options.iocharset); + fat_reset_iocharset(&sbi->options); kfree(sbi); }
@@ -1118,7 +1126,7 @@ static int parse_options(struct super_bl opts->fs_fmask = opts->fs_dmask = current_umask(); opts->allow_utime = -1; opts->codepage = fat_default_codepage; - opts->iocharset = fat_default_iocharset; + fat_reset_iocharset(opts); if (is_vfat) { opts->shortname = VFAT_SFN_DISPLAY_WINNT|VFAT_SFN_CREATE_WIN95; opts->rodir = 0; @@ -1275,8 +1283,7 @@ static int parse_options(struct super_bl
/* vfat specific */ case Opt_charset: - if (opts->iocharset != fat_default_iocharset) - kfree(opts->iocharset); + fat_reset_iocharset(opts); iocharset = match_strdup(&args[0]); if (!iocharset) return -ENOMEM; @@ -1867,8 +1874,7 @@ out_fail: iput(fat_inode); unload_nls(sbi->nls_io); unload_nls(sbi->nls_disk); - if (sbi->options.iocharset != fat_default_iocharset) - kfree(sbi->options.iocharset); + fat_reset_iocharset(&sbi->options); sb->s_fs_info = NULL; kfree(sbi); return error;