On 1/26/21 3:35 PM, Stefano Garzarella wrote:
> On Tue, Jan 26, 2021 at 12:18:47PM +0100, Philippe Mathieu-Daudé wrote:
>> QEMU fuzzer reported a buffer overflow in _eth_get_rss_ex_dst_addr()
>> reproducible as:
>>
>> $ cat << EOF | ./qemu-system-i386 -M pc-q35-5.0 \
>> -accel qtest -monitor none \
>> -serial none -nographic -qtest stdio
>> outl 0xcf8 0x80001010
>> outl 0xcfc 0xe1020000
>> outl 0xcf8 0x80001004
>> outw 0xcfc 0x7
>> write 0x25 0x1 0x86
>> write 0x26 0x1 0xdd
>> write 0x4f 0x1 0x2b
>> write 0xe1020030 0x4 0x190002e1
>> write 0xe102003a 0x2 0x0807
>> write 0xe1020048 0x4 0x12077cdd
>> write 0xe1020400 0x4 0xba077cdd
>> write 0xe1020420 0x4 0x190002e1
>> write 0xe1020428 0x4 0x3509d807
>> write 0xe1020438 0x1 0xe2
>> EOF
>> =================================================================
>> ==2859770==ERROR: AddressSanitizer: stack-buffer-overflow on address
>> 0x7ffdef904902 at pc 0x561ceefa78de bp 0x7ffdef904820 sp 0x7ffdef904818
>> READ of size 1 at 0x7ffdef904902 thread T0
>> #0 0x561ceefa78dd in _eth_get_rss_ex_dst_addr net/eth.c:410:17
>> #1 0x561ceefa41fb in eth_parse_ipv6_hdr net/eth.c:532:17
>> #2 0x561cef7de639 in net_tx_pkt_parse_headers
>> hw/net/net_tx_pkt.c:228:14
>> #3 0x561cef7dbef4 in net_tx_pkt_parse hw/net/net_tx_pkt.c:273:9
>> #4 0x561ceec29f22 in e1000e_process_tx_desc
>> hw/net/e1000e_core.c:730:29
>> #5 0x561ceec28eac in e1000e_start_xmit hw/net/e1000e_core.c:927:9
>> #6 0x561ceec1baab in e1000e_set_tdt hw/net/e1000e_core.c:2444:9
>> #7 0x561ceebf300e in e1000e_core_write hw/net/e1000e_core.c:3256:9
>> #8 0x561cef3cd4cd in e1000e_mmio_write hw/net/e1000e.c:110:5
>>
>> Address 0x7ffdef904902 is located in stack of thread T0 at offset 34
>> in frame
>> #0 0x561ceefa320f in eth_parse_ipv6_hdr net/eth.c:486
>>
>> This frame has 1 object(s):
>> [32, 34) 'ext_hdr' (line 487) <== Memory access at offset 34
>> overflows this variable
>> HINT: this may be a false positive if your program uses some custom
>> stack unwind mechanism, swapcontext or vfork
>> (longjmp and C++ exceptions *are* supported)
>> SUMMARY: AddressSanitizer: stack-buffer-overflow net/eth.c:410:17 in
>> _eth_get_rss_ex_dst_addr
>> Shadow bytes around the buggy address:
>> 0x10003df188d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 0x10003df188e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 0x10003df188f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 0x10003df18900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 0x10003df18910: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
>> =>0x10003df18920:[02]f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
>> 0x10003df18930: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 0x10003df18940: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 0x10003df18950: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 0x10003df18960: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> 0x10003df18970: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> Shadow byte legend (one shadow byte represents 8 application bytes):
>> Addressable: 00
>> Partially addressable: 01 02 03 04 05 06 07
>> Stack left redzone: f1
>> Stack right redzone: f3
>> ==2859770==ABORTING
>>
>> Similarly GCC 11 reports:
>>
>> net/eth.c: In function 'eth_parse_ipv6_hdr':
>> net/eth.c:410:15: error: array subscript 'struct
>> ip6_ext_hdr_routing[0]' is partly outside array bounds of 'struct
>> ip6_ext_hdr[1]' [-Werror=array-bounds]
>> 410 | if ((rthdr->rtype == 2) && (rthdr->segleft == 1)) {
>> | ~~~~~^~~~~~~
>> net/eth.c:485:24: note: while referencing 'ext_hdr'
>> 485 | struct ip6_ext_hdr ext_hdr;
>> | ^~~~~~~
>> net/eth.c:410:38: error: array subscript 'struct
>> ip6_ext_hdr_routing[0]' is partly outside array bounds of 'struct
>> ip6_ext_hdr[1]' [-Werror=array-bounds]
>> 410 | if ((rthdr->rtype == 2) && (rthdr->segleft == 1)) {
>> | ~~~~~^~~~~~~~~
>> net/eth.c:485:24: note: while referencing 'ext_hdr'
>> 485 | struct ip6_ext_hdr ext_hdr;
>> | ^~~~~~~
>>
>> In eth_parse_ipv6_hdr() we called iov_to_buf() to fill the 2 bytes of
>> the 'ext_hdr' buffer, then _eth_get_rss_ex_dst_addr() tries to access
>> beside the 2 filled bytes.
>>
>> Fix by reworking the function, filling the full rt_hdr buffer on the
>> stack calling iov_to_buf() again.
>>
>> Add the corresponding qtest case with the fuzzer reproducer.
>>
>> Cc: qemu-sta...@nongnu.org
>> Buglink: https://bugs.launchpad.net/qemu/+bug/1879531
>> Reported-by: Alexander Bulekov <alx...@bu.edu>
>> Reported-by: Miroslav Rezanina <mreza...@redhat.com>
>> Fixes: eb700029c78 ("net_pkt: Extend packet abstraction as required by
>> e1000e functionality")
>> Reviewed-by: Miroslav Rezanina <mreza...@redhat.com>
>> Acked-by: Thomas Huth <th...@redhat.com>
>> Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com>
>> ---
>> net/eth.c | 25 +++++++---------
>> tests/qtest/fuzz-e1000e-test.c | 53 ++++++++++++++++++++++++++++++++++
>> MAINTAINERS | 1 +
>> tests/qtest/meson.build | 1 +
>> 4 files changed, 66 insertions(+), 14 deletions(-)
>> create mode 100644 tests/qtest/fuzz-e1000e-test.c
>>
>> diff --git a/net/eth.c b/net/eth.c
>> index 7d4dd48c1ff..ae4db37888e 100644
>> --- a/net/eth.c
>> +++ b/net/eth.c
>> @@ -401,26 +401,23 @@ eth_is_ip6_extension_header_type(uint8_t hdr_type)
>>
>> static bool
>> _eth_get_rss_ex_dst_addr(const struct iovec *pkt, int pkt_frags,
>> - size_t rthdr_offset,
>> + size_t ext_hdr_offset,
>> struct ip6_ext_hdr *ext_hdr,
>> struct in6_address *dst_addr)
>> {
>> - struct ip6_ext_hdr_routing *rthdr = (struct ip6_ext_hdr_routing
>> *) ext_hdr;
>> + struct ip6_ext_hdr_routing rt_hdr;
>> + size_t input_size = iov_size(pkt, pkt_frags);
>> + size_t bytes_read;
>>
>> - if ((rthdr->rtype == 2) && (rthdr->segleft == 1)) {
>> + if (input_size < ext_hdr_offset + sizeof(rt_hdr)) {
>> + return false;
>> + }
>>
>> - size_t input_size = iov_size(pkt, pkt_frags);
>> - size_t bytes_read;
>> + bytes_read = iov_to_buf(pkt, pkt_frags, ext_hdr_offset,
>> + &rt_hdr, sizeof(rt_hdr));
>>
>> - if (input_size < rthdr_offset + sizeof(*ext_hdr)) {
>> - return false;
>> - }
>> -
>> - bytes_read = iov_to_buf(pkt, pkt_frags,
>> - rthdr_offset + sizeof(*ext_hdr),
>> - dst_addr, sizeof(*dst_addr));
>> -
>> - return bytes_read == sizeof(*dst_addr);
>> + if ((rt_hdr.rtype == 2) && (rt_hdr.segleft == 1)) {
>> + return bytes_read == sizeof(*ext_hdr) + sizeof(*dst_addr);
>
> Maybe I missed something but bytes_read can be at most 8,
> sizeof(*ext_hdr) should be 2 and sizeof(*dst_addr) should be 16, so IIUC
> this check is always false.
>
> Also, before this patch, the function filled dst_addr, now we don't, is
> that right?
Well I'll split in multiple trivial changes and KISS.
Thanks for the review!
Phil.
