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nemobis opened this issue Nov 20, 2019 · 6 comments
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Segmentation fault #900

nemobis opened this issue Nov 20, 2019 · 6 comments
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@nemobis
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nemobis commented Nov 20, 2019 •
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$ lscpu
Segmentation fault

lscpu from util-linux 2.33.1
Linux 4.14.154-grsec-kapsi #1 SMP Sat Nov 16 21:42:59 EET 2019 x86_64 GNU/Linux
Dell R6515: AMD EPYC 7402P 2,8 GHz 24C/48T

Cf. lscpu crashs when /dev/mem is not stable to read , lscpu crashes on certain arm64 devices. I cannot test with another kernel or higher privileges, sorry.
@karelzak karelzak added the NEEDINFO Need more information from reporter label Nov 20, 2019
@karelzak
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Can you try "strace -e open,openat lscpu"? It sounds you have no /sys/firmware/dmi/tables/DMI at all.

@karelzak
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And do you have /sys/firmware/efi directory?

It sounds like on your system lscpu don't found /sys/firmware/dmi/tables/DMI, and then it found efi (/sys/firmware/efi/systab) and and it tries to read /dev/mem according stuff from the firmware.

For example on Cortex-A9:

stat64("/sys/firmware/dmi/tables/DMI", 0xbeff8ef0) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/sys/firmware/efi/systab", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/proc/efi/systab", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file or directory)

this is expected (no efi, no dmi, ignore /dev/mem).

@karelzak
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karelzak commented Nov 20, 2019 •
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Uf, I see "AMD EPYC" ... it does not sound like ARM.

@nemobis
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nemobis commented Nov 20, 2019 via email

@karelzak
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It's expected that /sys/firmware/dmi/tables/DMI is readable for root only. In this case it falls back to EFI, and if EFI not readable than it tries some hardcoded addresses in /dev/mem (for x86_64 and i386). It should be visible in strace output.

It seems your kernel use grsecurity, maybe it's reason why you see the problem.

Anyway, we need more information -- why and where in code it segfault. For now it's too generic report :-)

@nemobis
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nemobis commented Nov 21, 2019

Anyway, we need more information -- why and where in code it segfault. For now it's too generic report :-)

Indeed, thank you. I'm only a user of this machine, so let's close this. If anyone in a similar situation is interested, now they know how to report it.

@nemobis nemobis closed this as completed Nov 21, 2019
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