On Wed, Nov 25, 2020 at 11:01:39AM +0100, Alexander Dahl wrote:
> 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.
Now queued up, thanks.
greg k-h
