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

Greg KH
2025-03-24T16:19:04Z

On Mon, Mar 24, 2025 at 07:14:07PM +0300, Cengiz Can wrote:
> On 20-03-25 20:30:15, Salvatore Bonaccorso wrote:
> > Hi
> >
>
> Hello Salvatore,
>
> > 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);
> > > }
>
> Simpler the better.
>
> Our fix was released back in February. (There are other issues in our attempt I
> admit).
>
> https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/jammy/commit/?id=2e8d8dffa2e0b5291522548309ec70428be7cf5a
>
> If someone can pick this submission, I will be happy to replace our version.

any specific reason why you didn't submit this upstream? Or did that
happen and it somehow not get picked up?

And why assign a CVE for an issue that is in the mainline kernel, last I
checked, Canonical was NOT allowed to do that.

Please work to revoke that CVE and ask for one properly.

thanks,

greg k-h