From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org,
syzbot <syzbot+90b8e10515ae88228a92@syzkaller.appspotmail.com>,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: [PATCH] fat: Fix memory allocation failure handling of match_strdup()
Date: Thu, 12 Jul 2018 15:15:19 +0900 [thread overview]
Message-ID: <8736wp9dzc.fsf@mail.parknet.co.jp> (raw)
In-Reply-To: <00000000000097c8ab0570bead4a@google.com> (syzbot's message of "Wed, 11 Jul 2018 12:59:02 -0700")
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.
Reported-by: syzbot+90b8e10515ae88228a92@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---
fs/fat/inode.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff -puN fs/fat/inode.c~fat-fix-kmalloc-failure fs/fat/inode.c
--- linux/fs/fat/inode.c~fat-fix-kmalloc-failure 2018-07-12 12:20:30.388600735 +0900
+++ linux-hirofumi/fs/fat/inode.c 2018-07-12 15:09:48.764070539 +0900
@@ -703,13 +703,21 @@ 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);
}
@@ -1124,7 +1132,7 @@ 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;
@@ -1281,8 +1289,7 @@ 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;
@@ -1873,8 +1880,7 @@ 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;
_
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
prev parent reply other threads:[~2018-07-12 6:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-11 19:59 KASAN: invalid-free in fat_fill_super syzbot
2018-07-12 6:15 ` OGAWA Hirofumi [this message]
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