Re: [PATCH] hfs/hfsplus: fix slab-out-of-bounds in hfs_bnode_read_key

[Salvatore Bonaccorso <carnil@debian.org>]

Hi

On Sat, Oct 19, 2024 at 10:13:03PM +0300, Vasiliy Kovalev wrote:
> Syzbot reported an issue in hfs subsystem:
> 
> BUG: KASAN: slab-out-of-bounds in memcpy_from_page include/linux/highmem.h:423 [inline]
> BUG: KASAN: slab-out-of-bounds in hfs_bnode_read fs/hfs/bnode.c:35 [inline]
> BUG: KASAN: slab-out-of-bounds in hfs_bnode_read_key+0x314/0x450 fs/hfs/bnode.c:70
> Write of size 94 at addr ffff8880123cd100 by task syz-executor237/5102
> 
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
>  print_address_description mm/kasan/report.c:377 [inline]
>  print_report+0x169/0x550 mm/kasan/report.c:488
>  kasan_report+0x143/0x180 mm/kasan/report.c:601
>  kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
>  __asan_memcpy+0x40/0x70 mm/kasan/shadow.c:106
>  memcpy_from_page include/linux/highmem.h:423 [inline]
>  hfs_bnode_read fs/hfs/bnode.c:35 [inline]
>  hfs_bnode_read_key+0x314/0x450 fs/hfs/bnode.c:70
>  hfs_brec_insert+0x7f3/0xbd0 fs/hfs/brec.c:159
>  hfs_cat_create+0x41d/0xa50 fs/hfs/catalog.c:118
>  hfs_mkdir+0x6c/0xe0 fs/hfs/dir.c:232
>  vfs_mkdir+0x2f9/0x4f0 fs/namei.c:4257
>  do_mkdirat+0x264/0x3a0 fs/namei.c:4280
>  __do_sys_mkdir fs/namei.c:4300 [inline]
>  __se_sys_mkdir fs/namei.c:4298 [inline]
>  __x64_sys_mkdir+0x6c/0x80 fs/namei.c:4298
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fbdd6057a99
> 
> Add a check for key length in hfs_bnode_read_key to prevent
> out-of-bounds memory access. If the key length is invalid, the
> key buffer is cleared, improving stability and reliability.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: syzbot+5f3a973ed3dfb85a6683@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=5f3a973ed3dfb85a6683
> Cc: stable@vger.kernel.org
> Signed-off-by: Vasiliy Kovalev <kovalev@altlinux.org>
> ---
>  fs/hfs/bnode.c     | 6 ++++++
>  fs/hfsplus/bnode.c | 6 ++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/fs/hfs/bnode.c b/fs/hfs/bnode.c
> index 6add6ebfef8967..cb823a8a6ba960 100644
> --- a/fs/hfs/bnode.c
> +++ b/fs/hfs/bnode.c
> @@ -67,6 +67,12 @@ void hfs_bnode_read_key(struct hfs_bnode *node, void *key, int off)
>  	else
>  		key_len = tree->max_key_len + 1;
>  
> +	if (key_len > sizeof(hfs_btree_key) || key_len < 1) {
> +		memset(key, 0, sizeof(hfs_btree_key));
> +		pr_err("hfs: Invalid key length: %d\n", key_len);
> +		return;
> +	}
> +
>  	hfs_bnode_read(node, key, off, key_len);
>  }
>  
> diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
> index 87974d5e679156..079ea80534f7de 100644
> --- a/fs/hfsplus/bnode.c
> +++ b/fs/hfsplus/bnode.c
> @@ -67,6 +67,12 @@ void hfs_bnode_read_key(struct hfs_bnode *node, void *key, int off)
>  	else
>  		key_len = tree->max_key_len + 2;
>  
> +	if (key_len > sizeof(hfsplus_btree_key) || key_len < 1) {
> +		memset(key, 0, sizeof(hfsplus_btree_key));
> +		pr_err("hfsplus: Invalid key length: %d\n", key_len);
> +		return;
> +	}
> +
>  	hfs_bnode_read(node, key, off, key_len);
>  }
>  
> -- 
> 2.33.8

I do realize that the HFS filesystem is "Orphan". But in the light of
the disclosure in
https://ssd-disclosure.com/ssd-advisory-linux-kernel-hfsplus-slab-out-of-bounds-write/
is there still something which needs to be done here?

Does the above needs to be picked in mainline and then propagated to
the supported stable versions?

Regards,
Salvatore