I'm noticing one small issue with this suggested patch: In file included from ../src_musl/src/internal/syscall.h:6, from ../src_musl/src/dirent/opendir.c:6: ../src_musl/arch/i386/syscall_arch.h: In function ‘__syscall0’: ../src_musl/arch/i386/syscall_arch.h:17:28: error: ‘ENOSYS’ undeclared (first use in this function) 17 | if (n>350) return -ENOSYS; | ^~~~~~ ../src_musl/arch/i386/syscall_arch.h:17:28: note: each undeclared identifier is reported only once for each function it appears in ../src_musl/arch/i386/syscall_arch.h: In function ‘__syscall1’: ../src_musl/arch/i386/syscall_arch.h:25:28: error: ‘ENOSYS’ undeclared (first use in this function) 25 | if (n>350) return -ENOSYS; | ^~~~~~ ../src_musl/arch/i386/syscall_arch.h: In function ‘__syscall2’: ../src_musl/arch/i386/syscall_arch.h:33:28: error: ‘ENOSYS’ undeclared (first use in this function) 33 | if (n>350) return -ENOSYS; Should we be adding an include or just defining this locally? Satadru On Thu, Feb 17, 2022 at 1:17 PM Rich Felker wrote: > On Thu, Feb 17, 2022 at 11:36:31AM -0500, Satadru Pramanik wrote: > > This machine is a EOL Samsung Series 5 Chromebook > > < > https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/samsung-series-5-chromebook/ > > > > code > > named Alex > > < > https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/#:~:text=Series%205%20Chromebook-,Alex,-x86%2Dalex%20%26%20x86 > > > > .. > > It is the target device for our i686 builds for Chromebrew. > > > > It is running a 3.8.11 kernel, and I believe the kernel source for that > is > > here: > > > https://chromium.googlesource.com/chromiumos/third_party/kernel/+/refs/heads/chromeos-3.8 > > > > Getting a signed kernel update for an EOL kernel for an EOL machine is > > close to impossible from Google, so we're just trying to work around > these > > If these are machines you're in control of, you may be able to load a > module to patch it. If this is something you're deploying to users > stuck on that kernel who don't want to fix their systems, then of > course that's not a practical option. > > > issues in userspace to maintain some functionality for any users who may > > still be using the device. > > > > The simplest workaround possible would be ideal. > > If you're shipping binaries specifically for these devices, the > simplest fix is just to emulate the failure that should happen in the > kernel in userspace, using the attached patch. DO NOT deploy this > patch in binaries meant to be used on modern systems, since they will > break when Y2038 rolls around. (Your old Chromebooks will break then > too.) > > > It is interesting though > > that the sample program works fine when built against near-stock glibc > > 2.23, no? > > No. If your kernel has a bug that makes something behave wildly wrong, > whether you do or don't see that as visible breakage with a particular > piece of software is not particularly interesting. > > I'm pretty sure, however, that you just haven't tested enough to see > any failures. glibc 2.23 is from 2016, so any functionality in it > using syscalls added after 2011 (3.8 kernel) is going to blow up > badly, thinking the syscall succeeded and returned some positive value > when actually the kernel lacks it. > > In the particular case of clock_gettime, it's just that your glibc > 2.23 has a hard Y2038 EOL and does not use/support the missing time64 > syscalls. > > > > On Thu, Feb 17, 2022 at 11:05 AM Rich Felker wrote: > > > > > On Thu, Feb 17, 2022 at 10:53:52AM -0500, Rich Felker wrote: > > > > On Thu, Feb 17, 2022 at 09:49:45AM -0500, Satadru Pramanik wrote: > > > > > Apologies for not being as familiar with gdb as I ought to be. > > > > > I used the __clock_gettime64 breakpoint and did a backtrace and > finish > > > > > repeatedly. > > > > > I couldn't figure out how to best get the timespec struct info. > > > > > > > > > > Alternately if you want to throw out a sample test program for me > to > > > build > > > > > and run, and what gdb commands to run to get the right info, happy > to > > > do > > > > > that too. > > > > > > > > > > gdb output is attached. > > > > > > > > If gdb reported it correctly, clock_gettime returned 403, which > should > > > > be impossible. It can only return 0 or -1. Incidentally, 403 is the > > > > syscall number for SYS_clock_gettime64, which suggests your kernel is > > > > simply *returning the syscall number* instead of -ENOSYS for syscalls > > > > that don't exist on it. Is this a stock kernel (3.8 IIRC) or does it > > > > have any sort of weird vendor patching? Any LSMs loaded? > > > > > > > > If you'd like to run a test just to make sure we're accurately seeing > > > > what's happening, the attached should work. It should print 0 > followed > > > > by the current time in seconds and nanoseconds. > > > > > > It looks like you hit the bug introduced in commit > > > 554086d85e71f30abe46fc014fea31929a7c6a8a and fixed in commit > > > 8142b215501f8b291a108a202b3a053a265b03dd. It looks like, since the > > > former was a CVE fix, somebody backported it to the kernel you're > > > using, but they failed to backport the fix-for-the-fix, so you have a > > > kernel that operates dangerously incorrectly for syscall numbers it's > > > unaware of. > > > > > > This really needs to be fixed in the kernel if you can. On our side > > > (musl) we probably need to find out if such kernels are actually out > > > in the wild, and if so, whether there's any reasonable way to detect > > > the false success and treat it as failure. > > > > > > > > On Thu, Feb 17, 2022 at 8:46 AM Rich Felker > wrote: > > > > > > > > > > > On Thu, Feb 17, 2022 at 08:30:47AM -0500, Satadru Pramanik wrote: > > > > > > > *This is a failure:* > > > > > > > tcpdump -i any -vvv host 192.168.0.115 > > > > > > > tcpdump: listening on any, link-type LINUX_SLL (Linux cooked > v1), > > > capture > > > > > > > size 262144 bytes > > > > > > > 08:29:38.043849 IP (tos 0x0, ttl 64, id 0, offset 0, flags > [DF], > > > proto > > > > > > UDP > > > > > > > (17), length 56) > > > > > > > 192.168.0.115.60625 > office.lan.53: [udp sum ok] 0+ A? > > > google.com. > > > > > > (28) > > > > > > > 08:29:38.044237 IP (tos 0x0, ttl 64, id 11463, offset 0, flags > > > [DF], > > > > > > proto > > > > > > > UDP (17), length 72) > > > > > > > office.lan.53 > 192.168.0.115.60625: [bad udp cksum 0x820a > -> > > > > > > 0x5c7d!] > > > > > > > 0 q: A? google.com. 1/0/0 google.com. [2m15s] A 142.250.80.110 > > > (44) > > > > > > > 08:29:38.047754 IP (tos 0x0, ttl 64, id 0, offset 0, flags > [DF], > > > proto > > > > > > UDP > > > > > > > (17), length 56) > > > > > > > 192.168.0.115.60625 > office.lan.53: [udp sum ok] 0+ AAAA? > > > > > > google.com. > > > > > > > (28) > > > > > > > 08:29:38.048078 IP (tos 0x0, ttl 64, id 11464, offset 0, flags > > > [DF], > > > > > > proto > > > > > > > UDP (17), length 84) > > > > > > > office.lan.53 > 192.168.0.115.60625: [bad udp cksum 0x8216 > -> > > > > > > 0xb42f!] > > > > > > > 0 q: AAAA? google.com. 1/0/0 google.com. [4m26s] AAAA > > > > > > > 2607:f8b0:4006:80d::200e (56) > > > > > > > 08:29:38.048955 IP (tos 0xc0, ttl 64, id 59728, offset 0, flags > > > [none], > > > > > > > proto ICMP (1), length 112) > > > > > > > 192.168.0.115 > office.lan: ICMP 192.168.0.115 udp port > 60625 > > > > > > > unreachable, length 92 > > > > > > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > > > > > > > > > OK, this shows that the client has requested both answers and the > > > > > > nameserver replied almost immediately (about 0.5ms later), but > when > > > > > > the second reply arrives (to the AAAA), the client has already > closed > > > > > > the listening port, despite only a few ms having passed. The > only way > > > > > > I see this could happen is by "timing out". This suggests that > > > > > > something is wrong with telling time. > > > > > > > > > > > > Can you either put a breakpoint in __clock_gettime64 (this is the > > > name > > > > > > you have to use for a breakpoint -- sorry I messed it up last > time) > > > > > > and then see what it returns when you "finish" it and what's in > the > > > > > > timespec struct after that? Or just write a test program to call > > > > > > clock_gettime(CLOCK_REALTIME, &ts) (note: you do NOT need or > want to > > > > > > use the time64 symbol name here) and print the results (return > value > > > > > > and contents of the timespec struct). > > > > > > > > > > > > > > > > > > > > > > > > > IP (tos 0x0, ttl 64, id 11464, offset 0, flags [DF], > proto > > > UDP > > > > > > > (17), length 84) > > > > > > > office.lan.53 > 192.168.0.115.60625: [udp sum ok] 0 q: > AAAA? > > > > > > google.com. > > > > > > > 1/0/0 google.com. [4m26s] AAAA 2607:f8b0:4006:80d::200e (56) > > > > > > > 08:29:39.476101 IP (tos 0x0, ttl 64, id 12690, offset 0, flags > > > [DF], > > > > > > proto > > > > > > > TCP (6), length 52) > > > > > > > 192.168.0.115.51204 > lga34s35-in-f3.1e100.net.80: Flags > [.], > > > cksum > > > > > > > 0xa666 (correct), seq 1466707759, ack 3358943837, win 115, > options > > > > > > > [nop,nop,TS val 198422160 ecr 2351261566], length 0 > > > > > > > 08:29:39.478914 IP (tos 0x80, ttl 122, id 6227, offset 0, flags > > > [none], > > > > > > > proto TCP (6), length 52) > > > > > > > lga34s35-in-f3.1e100.net.80 > 192.168.0.115.51204: Flags > [.], > > > cksum > > > > > > > 0xa5b7 (correct), seq 1, ack 1, win 282, options [nop,nop,TS > val > > > > > > 2351306585 > > > > > > > ecr 198377148], length 0 > > > > > > > ^C > > > > > > > 7 packets captured > > > > > > > 7 packets received by filter > > > > > > > 0 packets dropped by kernel > > > > > > > > > > > > > > > > > > > > > #include > > > > #include > > > > int main() > > > > { > > > > struct timespec ts; > > > > printf("%d", clock_gettime(CLOCK_REALTIME, &ts)); > > > > printf(" %lld %.9ld\n", (long long)ts.tv_sec, ts.tv_nsec); > > > > } > > > > > > >