From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: syzbot <syzbot+bca9799bf129256190da@syzkaller.appspotmail.com>
Cc: adilger.kernel@dilger.ca, akpm@linux-foundation.org,
dan.j.williams@intel.com, jack@suse.cz,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, syzkaller-bugs@googlegroups.com
Subject: Re: BUG: unable to handle kernel NULL pointer dereference in generic_perform_write (2)
Date: Wed, 15 Apr 2020 00:35:53 -0400 [thread overview]
Message-ID: <20200415043553.GH90651@mit.edu> (raw)
In-Reply-To: <00000000000016a67305a33a11f7@google.com>
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 5b8b9d0c6d0e0f1993c6c56deaf9646942c49d94
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9728e7b0e84f..e44fee317965 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1728,6 +1728,7 @@ static int clear_qf_name(struct super_block *sb, int qtype)
#define MOPT_NO_EXT3 0x0200
#define MOPT_EXT4_ONLY (MOPT_NO_EXT2 | MOPT_NO_EXT3)
#define MOPT_STRING 0x0400
+#define MOPT_NO_REMOUNT 0x0800
static const struct mount_opts {
int token;
@@ -1777,7 +1778,7 @@ static const struct mount_opts {
{Opt_min_batch_time, 0, MOPT_GTE0},
{Opt_inode_readahead_blks, 0, MOPT_GTE0},
{Opt_init_itable, 0, MOPT_GTE0},
- {Opt_dax, EXT4_MOUNT_DAX, MOPT_SET},
+ {Opt_dax, EXT4_MOUNT_DAX, MOPT_SET | MOPT_NO_REMOUNT},
{Opt_stripe, 0, MOPT_GTE0},
{Opt_resuid, 0, MOPT_GTE0},
{Opt_resgid, 0, MOPT_GTE0},
@@ -1819,7 +1820,7 @@ static const struct mount_opts {
{Opt_jqfmt_vfsv1, QFMT_VFS_V1, MOPT_QFMT},
{Opt_max_dir_size_kb, 0, MOPT_GTE0},
{Opt_test_dummy_encryption, 0, MOPT_GTE0},
- {Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET},
+ {Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET | MOPT_NO_REMOUNT},
{Opt_err, 0, 0}
};
@@ -1917,6 +1918,12 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
"Mount option \"%s\" incompatible with ext3", opt);
return -1;
}
+ if ((m->flags & MOPT_NO_REMOUNT) && is_remount) {
+ ext4_msg(sb, KERN_ERR,
+ "Mount option \"%s\" not supported when remounting",
+ opt);
+ return -1;
+ }
if (args->from && !(m->flags & MOPT_STRING) && match_int(args, &arg))
return -1;
@@ -5429,18 +5436,6 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
}
}
- if ((sbi->s_mount_opt ^ old_opts.s_mount_opt) & EXT4_MOUNT_NO_MBCACHE) {
- ext4_msg(sb, KERN_ERR, "can't enable nombcache during remount");
- err = -EINVAL;
- goto restore_opts;
- }
-
- if ((sbi->s_mount_opt ^ old_opts.s_mount_opt) & EXT4_MOUNT_DAX) {
- ext4_msg(sb, KERN_WARNING, "warning: refusing change of "
- "dax flag with busy inodes while remounting");
- sbi->s_mount_opt ^= EXT4_MOUNT_DAX;
- }
-
if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED)
ext4_abort(sb, EXT4_ERR_ESHUTDOWN, "Abort forced by user");
next prev parent reply other threads:[~2020-04-15 4:36 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-14 6:11 BUG: unable to handle kernel NULL pointer dereference in generic_perform_write (2) syzbot
2020-04-15 4:35 ` Theodore Y. Ts'o [this message]
2020-04-15 4:55 ` syzbot
2020-06-10 21:10 ` Theodore Y. Ts'o
2020-06-10 21:16 ` syzbot
2020-06-10 21:41 ` Theodore Y. Ts'o
2020-06-10 21:56 ` syzbot
2020-06-10 22:07 ` Theodore Y. Ts'o
2020-06-11 0:25 ` syzbot
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