From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-98647: bpf: Fix divide-by-zero in btf_struct_walk()
Date: Sun, 18 Oct 2026 17:18:31 +0200 [thread overview]
Message-ID: <2026101847-CVE-2026-98647-e686@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix divide-by-zero in btf_struct_walk()
When an access goes past the struct and the last member is a flexible
array, btf_struct_walk() folds the offset back into a single element with
(off - moff) % t->size, but never checks that the element type has a size.
BTF takes an empty struct, so this in program BTF
/* event could be empty */
struct event {
#ifdef HAVE_TIMESTAMP
__u64 ts;
#endif
};
struct batch {
int nr;
struct event events[];
};
divides by zero at prog load time. Getting there needs a PTR_TO_BTF_ID that
is not MEM_ALLOC, e.g. a plain read of a local kptr stashed in a map from a
sleepable program.
Oops: divide error: 0000 [#1] SMP KASAN PTI
RIP: 0010:btf_struct_walk+0x53f/0x1570
Call Trace:
<TASK>
btf_struct_access+0x42a/0xcd0
check_ptr_to_btf_access+0x4dc/0x1160
check_mem_access+0x3a45/0x8740
check_load_mem+0x36a/0xd10
do_check_common+0x3ef0/0xb210
bpf_check+0x6d3b/0x8580
bpf_prog_load+0xf7c/0x2720
__sys_bpf+0xa83/0x3690
__x64_sys_bpf+0xc7/0x150
x64_sys_call+0x1f3f/0x27e0
do_syscall_64+0xe5/0x610
entry_SYSCALL_64_after_hwframe+0x76/0x7e
</TASK>
Reject a zero-sized element type. The fixed array path in the same function
already bails out on the same thing:
btf_struct_walk()
...
/* skip empty array */
if (moff == mtrue_end)
continue;
msize /= total_nelems;
The Linux kernel CVE team has assigned CVE-2026-98647 to this issue.
Affected and fixed versions
===========================
Issue introduced in 5.8 with commit 9c5f8a1008a121e4c6b24af211034e24b0b63081 and fixed in 5.15.222 with commit 1ea3820937f8022e044c41c6e95c84b02741b45f
Issue introduced in 5.8 with commit 9c5f8a1008a121e4c6b24af211034e24b0b63081 and fixed in 6.1.189 with commit 172756f02663ad45c889c001c1a8cb4082a01a05
Issue introduced in 5.8 with commit 9c5f8a1008a121e4c6b24af211034e24b0b63081 and fixed in 6.6.158 with commit 934e9ba9f8d05656a48624710be67ca4dc8482e6
Issue introduced in 5.8 with commit 9c5f8a1008a121e4c6b24af211034e24b0b63081 and fixed in 6.12.112 with commit 63af086cb5fa6f72fd924f86bea4c2194da663a2
Issue introduced in 5.8 with commit 9c5f8a1008a121e4c6b24af211034e24b0b63081 and fixed in 6.18.55 with commit 8eb4cd72daad3a9ee63d2281bbdd16ce6d9406b1
Issue introduced in 5.8 with commit 9c5f8a1008a121e4c6b24af211034e24b0b63081 and fixed in 7.2.9 with commit b8fa56722e9c43bcd59c51fe4c7edd5f4158a11b
Issue introduced in 5.8 with commit 9c5f8a1008a121e4c6b24af211034e24b0b63081 and fixed in 7.3-rc5 with commit b0b3dc66529676228cb938cbcad66920f735c223
Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.
Unaffected versions might change over time as fixes are backported to
older supported kernel versions. The official CVE entry at
https://cve.org/CVERecord/?id=CVE-2026-98647
will be updated if fixes are backported, please check that for the most
up to date information about this issue.
Affected files
==============
The file(s) affected by this issue are:
kernel/bpf/btf.c
Mitigation
==========
The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes. Individual
changes are never tested alone, but rather are part of a larger kernel
release. Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all. If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
https://git.kernel.org/stable/c/1ea3820937f8022e044c41c6e95c84b02741b45f
https://git.kernel.org/stable/c/172756f02663ad45c889c001c1a8cb4082a01a05
https://git.kernel.org/stable/c/934e9ba9f8d05656a48624710be67ca4dc8482e6
https://git.kernel.org/stable/c/63af086cb5fa6f72fd924f86bea4c2194da663a2
https://git.kernel.org/stable/c/8eb4cd72daad3a9ee63d2281bbdd16ce6d9406b1
https://git.kernel.org/stable/c/b8fa56722e9c43bcd59c51fe4c7edd5f4158a11b
https://git.kernel.org/stable/c/b0b3dc66529676228cb938cbcad66920f735c223
reply other threads:[~2026-10-18 15:37 UTC|newest]
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