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[217.100.71.202]) by smtp.gmail.com with ESMTPSA id b49sm586004edc.51.2019.07.03.04.08.35 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 03 Jul 2019 04:08:36 -0700 (PDT) From: Frank de Brabander To: "David S . Miller" , Willem de Bruijn Cc: netdev@vger.kernel.org, Frank de Brabander Subject: bug: tpacket_snd can cause data corruption Date: Wed, 3 Jul 2019 13:07:08 +0200 Message-Id: <1562152028-2693-1-git-send-email-debrabander@gmail.com> X-Mailer: git-send-email 2.7.4 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org In commit 5cd8d46e a fix was applied for data corruption in tpacket_snd. A selftest was added in commit 358be656 which validates this fix. Unfortunately this bug still persists, although since this fix less likely to trigger. This bug was initially observed using a PACKET_MMAP application, but can also be seen by tweaking the kernel selftest. By tweaking the selftest txring_overwrite.c to run as an infinite loop, the data corruption will still trigger. It seems to occur faster by generating interrupts (e.g. by plugging in USB devices). Tested with kernel version 5.2-RC7. Cause for this bug is still unclear. Signed-off-by: Frank de Brabander --- tools/testing/selftests/net/txring_overwrite.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/net/txring_overwrite.c b/tools/testing/selftests/net/txring_overwrite.c index fd8b1c6..3ee23e5 100644 --- a/tools/testing/selftests/net/txring_overwrite.c +++ b/tools/testing/selftests/net/txring_overwrite.c @@ -143,19 +143,22 @@ static int read_verify_pkt(int fdr, char payload_char) int ret; ret = read(fdr, buf, sizeof(buf)); - if (ret != sizeof(buf)) - error(1, errno, "read"); + if (ret != sizeof(buf)) { + //error(1, errno, "read"); + printf("read error\n"); + return 1; + } if (buf[60] != payload_char) { printf("wrong pattern: 0x%x != 0x%x\n", buf[60], payload_char); return 1; } - printf("read: %c (0x%x)\n", buf[60], buf[60]); + //printf("read: %c (0x%x)\n", buf[60], buf[60]); return 0; } -int main(int argc, char **argv) +void run_test(void) { const char payload_patterns[] = "ab"; char *ring; @@ -177,3 +180,10 @@ int main(int argc, char **argv) return ret; } + +int main(int argc, char **argv) +{ + while (true) { + run_test(); + } +} -- 2.7.4