* [PATCH v1] bcachefs: set freespace inited to false if trans_mark_dev_sbs fails
@ 2024-10-20 17:08 Piotr Zalewski
2024-10-20 23:23 ` Kent Overstreet
0 siblings, 1 reply; 3+ messages in thread
From: Piotr Zalewski @ 2024-10-20 17:08 UTC (permalink / raw)
To: kent.overstreet, linux-bcachefs, linux-kernel
Cc: skhan, Piotr Zalewski, syzbot+2b6a17991a6af64f9489
In bch2_fs_initialize if bch2_trans_mark_dev_sbs fails, set freespace
initialized bits to 0 in member's flags and update member cached version
for each device. bch2_trans_mark_dev_sbs fails just before freespace
init which can left freespace init bits set to true erroneously which later
can indirectly trigger BUG condition in bch2_bucket_alloc_freelist[1].
[1] https://syzkaller.appspot.com/bug?extid=2b6a17991a6af64f9489
Reported-by: syzbot+2b6a17991a6af64f9489@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2b6a17991a6af64f9489
Fixes: bbe682c76789 ("bcachefs: Ensure devices are always correctly initialized")
Signed-off-by: Piotr Zalewski <pZ010001011111@proton.me>
---
fs/bcachefs/recovery.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c
index 67bba156cce9..bcec79122f65 100644
--- a/fs/bcachefs/recovery.c
+++ b/fs/bcachefs/recovery.c
@@ -1031,6 +1031,7 @@ int bch2_fs_initialize(struct bch_fs *c)
struct bkey_inode_buf packed_inode;
struct qstr lostfound = QSTR("lost+found");
int ret;
+ struct bch_member *m;
bch_notice(c, "initializing new filesystem");
set_bit(BCH_FS_new_fs, &c->flags);
@@ -1086,8 +1087,17 @@ int bch2_fs_initialize(struct bch_fs *c)
bch_verbose(c, "marking superblocks");
ret = bch2_trans_mark_dev_sbs(c);
bch_err_msg(c, ret, "marking superblocks");
- if (ret)
+ if (ret) {
+ mutex_lock(&c->sb_lock);
+ for_each_member_device(c, ca) {
+ m = bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
+ SET_BCH_MEMBER_FREESPACE_INITIALIZED(m, false);
+ ca->mi = bch2_mi_to_cpu(m);
+ }
+ mutex_unlock(&c->sb_lock);
+
goto err;
+ }
for_each_online_member(c, ca)
ca->new_fs_bucket_idx = 0;
--
2.47.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v1] bcachefs: set freespace inited to false if trans_mark_dev_sbs fails
2024-10-20 17:08 [PATCH v1] bcachefs: set freespace inited to false if trans_mark_dev_sbs fails Piotr Zalewski
@ 2024-10-20 23:23 ` Kent Overstreet
2024-10-21 8:05 ` Piotr Zalewski
0 siblings, 1 reply; 3+ messages in thread
From: Kent Overstreet @ 2024-10-20 23:23 UTC (permalink / raw)
To: Piotr Zalewski
Cc: linux-bcachefs, linux-kernel, skhan, syzbot+2b6a17991a6af64f9489
On Sun, Oct 20, 2024 at 05:08:45PM +0000, Piotr Zalewski wrote:
> In bch2_fs_initialize if bch2_trans_mark_dev_sbs fails, set freespace
> initialized bits to 0 in member's flags and update member cached version
> for each device. bch2_trans_mark_dev_sbs fails just before freespace
> init which can left freespace init bits set to true erroneously which later
> can indirectly trigger BUG condition in bch2_bucket_alloc_freelist[1].
Err...
freespace_initialized shouldn't even be set at this point, it's set
later, in bch2_fs_freespace_init(), naturally.
So - syzbot is feeding us garbage, heh. BCH_MEMBER_FREESPACE_INITIALIZED
should be false on a non initialized filesystem.
So we actually should be unconditially clearing it (sanitizing our
input) at the top of bch2_fs_initialize().
>
> [1] https://syzkaller.appspot.com/bug?extid=2b6a17991a6af64f9489
>
> Reported-by: syzbot+2b6a17991a6af64f9489@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=2b6a17991a6af64f9489
> Fixes: bbe682c76789 ("bcachefs: Ensure devices are always correctly initialized")
> Signed-off-by: Piotr Zalewski <pZ010001011111@proton.me>
> ---
> fs/bcachefs/recovery.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c
> index 67bba156cce9..bcec79122f65 100644
> --- a/fs/bcachefs/recovery.c
> +++ b/fs/bcachefs/recovery.c
> @@ -1031,6 +1031,7 @@ int bch2_fs_initialize(struct bch_fs *c)
> struct bkey_inode_buf packed_inode;
> struct qstr lostfound = QSTR("lost+found");
> int ret;
> + struct bch_member *m;
>
> bch_notice(c, "initializing new filesystem");
> set_bit(BCH_FS_new_fs, &c->flags);
> @@ -1086,8 +1087,17 @@ int bch2_fs_initialize(struct bch_fs *c)
> bch_verbose(c, "marking superblocks");
> ret = bch2_trans_mark_dev_sbs(c);
> bch_err_msg(c, ret, "marking superblocks");
> - if (ret)
> + if (ret) {
> + mutex_lock(&c->sb_lock);
> + for_each_member_device(c, ca) {
> + m = bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
> + SET_BCH_MEMBER_FREESPACE_INITIALIZED(m, false);
> + ca->mi = bch2_mi_to_cpu(m);
> + }
> + mutex_unlock(&c->sb_lock);
> +
> goto err;
> + }
>
> for_each_online_member(c, ca)
> ca->new_fs_bucket_idx = 0;
> --
> 2.47.0
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v1] bcachefs: set freespace inited to false if trans_mark_dev_sbs fails
2024-10-20 23:23 ` Kent Overstreet
@ 2024-10-21 8:05 ` Piotr Zalewski
0 siblings, 0 replies; 3+ messages in thread
From: Piotr Zalewski @ 2024-10-21 8:05 UTC (permalink / raw)
To: Kent Overstreet
Cc: linux-bcachefs, linux-kernel, skhan, syzbot+2b6a17991a6af64f9489
Hi Kent,
On Monday, October 21st, 2024 at 1:23 AM, Kent Overstreet <kent.overstreet@linux.dev> wrote:
> On Sun, Oct 20, 2024 at 05:08:45PM +0000, Piotr Zalewski wrote:
>
> > In bch2_fs_initialize if bch2_trans_mark_dev_sbs fails, set freespace
> > initialized bits to 0 in member's flags and update member cached version
> > for each device. bch2_trans_mark_dev_sbs fails just before freespace
> > init which can left freespace init bits set to true erroneously which later
> > can indirectly trigger BUG condition in bch2_bucket_alloc_freelist[1].
>
>
> Err...
>
> freespace_initialized shouldn't even be set at this point, it's set
> later, in bch2_fs_freespace_init(), naturally.
>
> So - syzbot is feeding us garbage, heh. BCH_MEMBER_FREESPACE_INITIALIZED
> should be false on a non initialized filesystem.
>
> So we actually should be unconditially clearing it (sanitizing our
> input) at the top of bch2_fs_initialize().
Initially I added it at the beginning of bch2_fs_initialize. I changed it
to here since then the error triggered is ENOSPC_disk_reservation instead
of EIO. I thought that it's somewhat important to retain the error so moved
it to the if statement.
I will move it to the sb_lock at the top. After syzbot tests it I will send
v2.
> > [1] https://syzkaller.appspot.com/bug?extid=2b6a17991a6af64f9489
> >
> > Reported-by: syzbot+2b6a17991a6af64f9489@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=2b6a17991a6af64f9489
> > Fixes: bbe682c76789 ("bcachefs: Ensure devices are always correctly initialized")
> > Signed-off-by: Piotr Zalewski pZ010001011111@proton.me
> > ---
> > fs/bcachefs/recovery.c | 12 +++++++++++-
> > 1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c
> > index 67bba156cce9..bcec79122f65 100644
> > --- a/fs/bcachefs/recovery.c
> > +++ b/fs/bcachefs/recovery.c
> > @@ -1031,6 +1031,7 @@ int bch2_fs_initialize(struct bch_fs *c)
> > struct bkey_inode_buf packed_inode;
> > struct qstr lostfound = QSTR("lost+found");
> > int ret;
> > + struct bch_member *m;
> >
> > bch_notice(c, "initializing new filesystem");
> > set_bit(BCH_FS_new_fs, &c->flags);
> > @@ -1086,8 +1087,17 @@ int bch2_fs_initialize(struct bch_fs *c)
> > bch_verbose(c, "marking superblocks");
> > ret = bch2_trans_mark_dev_sbs(c);
> > bch_err_msg(c, ret, "marking superblocks");
> > - if (ret)
> > + if (ret) {
> > + mutex_lock(&c->sb_lock);
> > + for_each_member_device(c, ca) {
> > + m = bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
> > + SET_BCH_MEMBER_FREESPACE_INITIALIZED(m, false);
> > + ca->mi = bch2_mi_to_cpu(m);
> > + }
> > + mutex_unlock(&c->sb_lock);
> > +
> > goto err;
> > + }
> >
> > for_each_online_member(c, ca)
> > ca->new_fs_bucket_idx = 0;
> > --
> > 2.47.0
Best regards, Piotr Zalewski
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-10-20 17:08 [PATCH v1] bcachefs: set freespace inited to false if trans_mark_dev_sbs fails Piotr Zalewski
2024-10-20 23:23 ` Kent Overstreet
2024-10-21 8:05 ` Piotr Zalewski
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