On 23/10/24 23:30, Gianfranco Trad wrote:
Add check on layout->sb_max_size_bits against BCH_SB_LAYOUT_SIZE_BITS_MAX
to prevent UBSAN shift-out-of-bounds in validate_sb_layout().
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")
Tested-by: [email protected]
Signed-off-by: Gianfranco Trad <[email protected]>
---
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]);
Wondering if this other patch might be considered more correct to
prevent shift oob, given also [0]:
diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index ce7410d72089..428172897501 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -287,7 +287,7 @@ static int validate_sb_layout(struct bch_sb_layout
*layout, struct printbuf *out
return -BCH_ERR_invalid_sb_layout_nr_superblocks;
}
- max_sectors = 1 << layout->sb_max_size_bits;
+ max_sectors = 1 << min(BCH_SB_LAYOUT_SIZE_BITS_MAX,
layout->sb_max_size_bits);
prev_offset = le64_to_cpu(layout->sb_offset[0]);
Also this patch was already tested by syzbot [1]
[0] 71dac2482ad3c8d4a8b8998a96751f009bad895f ("bcachefs:
BCH_SB_LAYOUT_SIZE_BITS_MAX")
[1] https://syzkaller.appspot.com/x/log.txt?x=1640b640580000
Thanks for your time,
-- Gian
