Greg KH wrote:
On Thu, Apr 21, 2016 at 11:18:16AM +0200, Martin MOKREJŠ wrote:
Hi Greg,
thank you for your answer.
Greg KH wrote:
On Thu, Apr 21, 2016 at 12:22:49AM +0200, Martin MOKREJŠ wrote:
Hi,
I am not certain to to forward this to, so I am trying linux-usb and ext4. Please add relevant people/lists, thank you.
# dmesg | grep "UBSAN: Undefined behaviour"
[ 2.638843] UBSAN: Undefined behaviour in drivers/usb/host/ehci-hub.c:873:47
[ 8.553620] UBSAN: Undefined behaviour in fs/ext4/mballoc.c:2612:15
[ 25.341048] UBSAN: Undefined behaviour in fs/ext4/mballoc.c:1274:11
[ 41.460542] UBSAN: Undefined behaviour in ./arch/x86/include/asm/atomic.h:156:9
#
Full dmesg is attached.
Hope this helps,
Martin
[ 0.000000] Linux version 4.5.1-default-pciehp (root@vostro) (gcc version 5.3.0 (Gentoo 5.3.0 p1.0, pie-0.6.5) ) #1 SMP Thu Apr 14 14:17:48 CEST 2016
Please try 4.6-rc4, a number of UBSAN issues have been fixed there.
They are still present:
# dmesg | grep "UBSAN: Undefined behaviour"
[ 3.113405] UBSAN: Undefined behaviour in drivers/usb/host/ehci-hub.c:877:47
[ 5.678949] UBSAN: Undefined behaviour in fs/ext4/mballoc.c:2619:15
[ 18.345599] UBSAN: Undefined behaviour in fs/ext4/mballoc.c:1281:11
[ 34.544363] UBSAN: Undefined behaviour in ./arch/x86/include/asm/atomic.h:156:9
Ah, sorry about that, turns out this is a bug in the tool, not in the
code, see the thread from a few weeks ago in the linux-usb archives with
the subject:
Subject: function ehci_hub_control in ehci-hub.c
for all of the details.
Thank you. I am not a programmer so I only infer from this thread I should disable
the UBSAN in .config. The kernel code is technically correct but triggers false alarm.
Maybe the UBSAN could have a whitelist of falsely matching locations?
https://www.mail-archive.com/linux-usb@xxxxxxxxxxxxxxx/msg72438.html
Did anybody check the ext4 code or is it also just believed the UBSAN complaint is
just broken and code changes are not necessary?
Martin
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