On Sat, Oct 26, 2024 at 09:09:53AM +0800, Lizhi Xu wrote: > Syzbot reported a slab-use-after-free Read in bch2_reconstruct_alloc. > The sb counters resize will cause sb reallocation and release the old sb, > which leads to uaf in ext. > After disk_sb.sb is reallocated, ext should be retrieved again to avoid uaf. > > Reported-and-tested-by: [email protected] > Closes: https://syzkaller.appspot.com/bug?extid=9fc4dac4775d07bcfe34 > Signed-off-by: Lizhi Xu <[email protected]> > --- > fs/bcachefs/recovery.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c > index 55e1504a8130..9df0969c29ce 100644 > --- a/fs/bcachefs/recovery.c > +++ b/fs/bcachefs/recovery.c > @@ -59,6 +59,7 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) > > mutex_lock(&c->sb_lock); > struct bch_sb_field_ext *ext = bch2_sb_field_get(c->disk_sb.sb, ext); > + void *sb; > > __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_allocations, > ext->recovery_passes_required); > __set_bit_le64(BCH_RECOVERY_PASS_STABLE_check_alloc_info, > ext->recovery_passes_required); > @@ -94,7 +95,10 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) > __set_bit_le64(BCH_FSCK_ERR_accounting_mismatch, ext->errors_silent); > c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info); > > + sb = c->disk_sb.sb; > bch2_write_super(c); > + if (sb != c->disk_sb.sb) > + ext = bch2_sb_field_get(c->disk_sb.sb, ext); > mutex_unlock(&c->sb_lock); > > c->opts.recovery_passes |= > bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0]));
There's a simpler fix: >From 8e910ca20e112d7f06ba3bf631a06ddb5ce14657 Mon Sep 17 00:00:00 2001 From: Kent Overstreet <[email protected]> Date: Fri, 25 Oct 2024 13:13:05 -0400 Subject: [PATCH] bcachefs: Fix UAF in bch2_reconstruct_alloc() write_super() -> sb_counters_from_cpu() may reallocate the superblock Reported-by: [email protected] Signed-off-by: Kent Overstreet <[email protected]> diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c index 454b5a32dd7f..0ebc76dd7eb5 100644 --- a/fs/bcachefs/recovery.c +++ b/fs/bcachefs/recovery.c @@ -94,11 +94,10 @@ static void bch2_reconstruct_alloc(struct bch_fs *c) __set_bit_le64(BCH_FSCK_ERR_accounting_mismatch, ext->errors_silent); c->sb.compat &= ~(1ULL << BCH_COMPAT_alloc_info); - bch2_write_super(c); - mutex_unlock(&c->sb_lock); - c->opts.recovery_passes |= bch2_recovery_passes_from_stable(le64_to_cpu(ext->recovery_passes_required[0])); + bch2_write_super(c); + mutex_unlock(&c->sb_lock); bch2_shoot_down_journal_keys(c, BTREE_ID_alloc, 0, BTREE_MAX_DEPTH, POS_MIN, SPOS_MAX);
