Hei hei,
please apply e9a6882f267a8105461066e3ea6b4b6b9be1b807 ("perf event: Check
ref_reloc_sym before using it") to the v4.9 stable tree and maybe to later LTS
trees (v4.14, v4.19) as well.
That change is in mainline since v5.4-rc1 and it's a fix for a possible null
pointer dereference in the tool 'perf', so it is a fix for a user space tool
coming with the kernel tree actually.
I am directly affeted by this, calling 'perf record' on an at91 based device
(armv5te, sam9g20 soc) running PREEMPT RT kernel 4.9.220-rt143 results in a
segfault here. I debugged this with gdb and tracked it down to the exact
pointer being NULL, which is checked now in that above mentioned changeset.
I could cleanly apply that changeset to my local tree and the segfault is not
triggered anymore, I can use perf on that platform now.
I only tested this on the above mentioned v4.9 based kernel version.
Thanks & Greets
Alex
