b54ba0dc0d
commit e608f631f0ba5f1fc5ee2e260a3a35d13107cbfe upstream. syzbot reported following splat: BUG: KASAN: vmalloc-out-of-bounds in size_entry_mwt net/bridge/netfilter/ebtables.c:2063 [inline] BUG: KASAN: vmalloc-out-of-bounds in compat_copy_entries+0x128b/0x1380 net/bridge/netfilter/ebtables.c:2155 Read of size 4 at addr ffffc900004461f4 by task syz-executor267/7937 CPU: 1 PID: 7937 Comm: syz-executor267 Not tainted 5.5.0-rc1-syzkaller #0 size_entry_mwt net/bridge/netfilter/ebtables.c:2063 [inline] compat_copy_entries+0x128b/0x1380 net/bridge/netfilter/ebtables.c:2155 compat_do_replace+0x344/0x720 net/bridge/netfilter/ebtables.c:2249 compat_do_ebt_set_ctl+0x22f/0x27e net/bridge/netfilter/ebtables.c:2333 [..] Because padding isn't considered during computation of ->buf_user_offset, "total" is decremented by fewer bytes than it should. Therefore, the first part of if (*total < sizeof(*entry) || entry->next_offset < sizeof(*entry)) will pass, -- it should not have. This causes oob access: entry->next_offset is past the vmalloced size. Reject padding and check that computed user offset (sum of ebt_entry structure plus all individual matches/watchers/targets) is same value that userspace gave us as the offset of the next entry. Reported-by: syzbot+f68108fed972453a0ad4@syzkaller.appspotmail.com Fixes: 81e675c227ec ("netfilter: ebtables: add CONFIG_COMPAT support") Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.