[SRU][F][PATCH 0/2] CVE-2024-26640

[Koichiro Den]

[Impact]

tcp: add sanity checks to rx zerocopy

TCP rx zerocopy intent is to map pages initially allocated
from NIC drivers, not pages owned by a fs.

This patch adds to can_map_frag() these additional checks:

- Page must not be a compound one.
- page->mapping must be NULL.

This fixes the panic reported by ZhangPeng.

syzbot was able to loopback packets built with sendfile(),
mapping pages owned by an ext4 file to TCP rx zerocopy.

r3 = socket$inet_tcp(0x2, 0x1, 0x0)
mmap(&(0x7f0000ff9000/0x4000)=nil, 0x4000, 0x0, 0x12, r3, 0x0)
r4 = socket$inet_tcp(0x2, 0x1, 0x0)
bind$inet(r4, &(0x7f0000000000)={0x2, 0x4e24, @multicast1}, 0x10)
connect$inet(r4, &(0x7f00000006c0)={0x2, 0x4e24, @empty}, 0x10)
r5 = openat$dir(0xffffffffffffff9c, &(0x7f00000000c0)='./file0\x00',
    0x181e42, 0x0)
fallocate(r5, 0x0, 0x0, 0x85b8)
sendfile(r4, r5, 0x0, 0x8ba0)
getsockopt$inet_tcp_TCP_ZEROCOPY_RECEIVE(r4, 0x6, 0x23,
    &(0x7f00000001c0)={&(0x7f0000ffb000/0x3000)=nil, 0x3000, 0x0, 0x0, 0x0,
    0x0, 0x0, 0x0, 0x0}, &(0x7f0000000440)=0x40)
r6 = openat$dir(0xffffffffffffff9c, &(0x7f00000000c0)='./file0\x00',
    0x181e42, 0x0)

[Backport]

The primary fix commit 577e4432f3ac ("tcp: add sanity checks to rx
zerocopy") depends on commit 98917cf0d6ed ("net-zerocopy: Refactor
frag-is-remappable test"). I backported it as it solely involves
refactoring without introducing new features, is compact enough, and
enables a clean cherry-pick of the primary fix.

[Fix]

Noble:  not affected
Jammy:  fixed via stable
Focal:  Backport - one dependent commit backported as well, see [Backport]
Bionic: not affected
Xenial: not affected
Trusty: not affected

[Test Case]

Compile and boot tested.

[Where problems could occur]

This fix affects those who use TCP_ZEROCOPY_RECEIVE feature, an issue
with this fix would be visible to use via system crash.


Arjun Roy (1):
  net-zerocopy: Refactor frag-is-remappable test.

Eric Dumazet (1):
  tcp: add sanity checks to rx zerocopy

 net/ipv4/tcp.c | 44 ++++++++++++++++++++++++++++++++++++--------
 1 file changed, 36 insertions(+), 8 deletions(-)

-- 
2.43.0