Date: Wed, 08 Jun 2022 20:21:48 -0700 From: Neel Chauhan <nc@FreeBSD.org> To: freebsd-hackers@freebsd.org Subject: Potential USB bug with read() (while updating android-tools-adb) Message-ID: <9b3dbdddb02e65c5ff4b3dc0f117c3c6@neelc.org>
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Hi hackers@, While attempting to update android-tools-(fastboot/adb) to a newer version, I noticed a potential bug with the FreeBSD USB subsystem. After two reads from a particular function in a USB device, read() reads 0 bytes even with it should read 8 bytes and returns 0 respectively instead of 8. The branch is: https://github.com/neelchauhan/freebsd-android-tools/tree/fbsd-31.0.3p1 The offending lines are: vendor/adb/client/commandline.cpp:928 (ReadFdExactly call) vendor/adb/adb_io.cpp:83 (adb_read call) vendor/adb/sysdeps.h:526 (adb_read definition, this calls read()) This happens when I attempt to flash LineageOS 19.1 (Android Custom ROM) to a Google Pixel 3 smartphone via the so-called "recovery", which is the "test" device used to test if this port works (my main device, a Google Pixel 6 Pro while rooted can't be used since I'm not willing to live without a phone). On Android, recoveries are used to update, root, or replace an Android installation. The `adb sideload` in the recovery causes read() to fail prematurely, whereas `adb push` in a recovery works perfectly. However, LineageOS requires the "sideload" function to install on many devices, and I don't want a broken port in the Ports tree either. On FreeBSD, this exact adb_read() routine works fine on other `adb` calls. On Linux (or macOS when I had a M1 Mac Mini before donating it to kevans@), `adb sideload` works perfectly, period. I doubt most of you are rooted Android users, so if you need help understanding how Android flashing works feel free to ping me, I'm no "expert" either but have been doing this for 8+ years. This error also happens with the Ports version, which is why I initially wanted to update. Is there anything FreeBSD does in its USB implementation that's funky, or even in libusb? Especially in the last 2-3 year? Or is it more adb issues. I am using an AMD Ryzen 5800X-based HP Omen 30L running FreeBSD 14.0-CURRENT with Git revision 0817c8dc2a4 (May 14), but this also happens on other Intel-based and AMD-based systems, with both USB-A and USB-C Ports. I'm not *really* a kernel person, and not at all a USB hacker. I'll probably update my CURRENT but this issue has been happening for 2 or so years now and rebooting into Linux USBs isn't exactly fun to flash my Android. -Neel (nc@)
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