Re: [PATCH v2] hfs/hfsplus: fix slab-out-of-bounds in hfs_bnode_read_key

[Attila Szasz <szasza.contact@gmail.com>]

This is exploitable for LPE and it should be fixed.

On 12/7/24 13:17, 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 validation for key length in hfs_bnode_read_key to prevent
> out-of-bounds memory access. Invalid key lengths, likely caused
> by corrupted file system images (potentially due to malformed
> data during image generation), now result in clearing the key
> buffer, enhancing 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>
> ---
> v2: add more information to the commit message regarding the purpose of the patch.
> ---
>   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);
>   }
>