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