Re: [syzbot] [bcachefs?] UBSAN: shift-out-of-bounds in validate_sb_layout

Gianfranco Trad
2024-10-23T21:08:35Z

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#syz test

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From c6d6215d66e9bd3d10a11a8b940246fda0494f30 Mon Sep 17 00:00:00 2001
From: Gianfranco Trad <gianf.trad@gmail.com>
Date: Wed, 23 Oct 2024 23:01:11 +0200
Subject: [PATCH] bcachefs: Fix invalid shift in validate_sb_layout()

Signed-off-by: Gianfranco Trad <gianf.trad@gmail.com>
---
fs/bcachefs/errcode.h | 1 +
fs/bcachefs/super-io.c | 5 +++++
2 files changed, 6 insertions(+)

diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
index 649263516ab1..b6cbd716000b 100644
--- a/fs/bcachefs/errcode.h
+++ b/fs/bcachefs/errcode.h
@@ -222,6 +222,7 @@
x(BCH_ERR_invalid_sb_layout, invalid_sb_layout_type) \
x(BCH_ERR_invalid_sb_layout, invalid_sb_layout_nr_superblocks) \
x(BCH_ERR_invalid_sb_layout, invalid_sb_layout_superblocks_overlap) \
+ x(BCH_ERR_invalid_sb_layout, invalid_sb_layout_sb_max_size_bits) \
x(BCH_ERR_invalid_sb, invalid_sb_members_missing) \
x(BCH_ERR_invalid_sb, invalid_sb_members) \
x(BCH_ERR_invalid_sb, invalid_sb_disk_groups) \
diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index ce7410d72089..44d0ac9b00dd 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -287,6 +287,11 @@ static int validate_sb_layout(struct bch_sb_layout *layout, struct printbuf *out
return -BCH_ERR_invalid_sb_layout_nr_superblocks;
}

+ if (layout->sb_max_size_bits > BCH_SB_LAYOUT_SIZE_BITS_MAX) {
+ prt_printf(out, "Invalid superblock layout: max_size_bits too high");
+ return -BCH_ERR_invalid_sb_layout_sb_max_size_bits;
+ }
+
max_sectors = 1 << layout->sb_max_size_bits;

prev_offset = le64_to_cpu(layout->sb_offset[0]);
--
2.43.0