[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <be3e7378-7aec-4ebb-b6e6-e7b824452adb@gmail.com>
Date: Thu, 24 Oct 2024 12:48:30 +0200
From: Gianfranco Trad <gianf.trad@...il.com>
To: kent.overstreet@...ux.dev
Cc: linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org,
skhan@...uxfoundation.org,
syzbot+089fad5a3a5e77825426@...kaller.appspotmail.com
Subject: Re: [PATCH] bcachefs: Fix invalid shift in validate_sb_layout()
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: syzbot+089fad5a3a5e77825426@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
> Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")
> Tested-by: syzbot+089fad5a3a5e77825426@...kaller.appspotmail.com
> Signed-off-by: Gianfranco Trad <gianf.trad@...il.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]);
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
Powered by blists - more mailing lists