On Tue, 2017-04-11 at 05:08:13 UTC, Ravi Bangoria wrote: > If we set a kprobe on a 'stdu' instruction on powerpc64, we see a kernel > OOPS: > > [ 1275.165932] Bad kernel stack pointer cd93c840 at c000000000009868 > [ 1275.166378] Oops: Bad kernel stack pointer, sig: 6 [#1] > ... > GPR00: c000001fcd93cb30 00000000cd93c840 c0000000015c5e00 00000000cd93c840 > ... > [ 1275.178305] NIP [c000000000009868] resume_kernel+0x2c/0x58 > [ 1275.178594] LR [c000000000006208] program_check_common+0x108/0x180 > > Basically, on 64 bit system, when user probes on 'stdu' instruction, > kernel does not emulate actual store in emulate_step itself because it > may corrupt exception frame. So kernel does actual store operation in > exception return code i.e. resume_kernel(). > > resume_kernel() loads the saved stack pointer from memory using lwz, > effectively loading a corrupt (32bit) address, causing the kernel crash. > > Fix this by loading the 64bit value instead. > > Fixes: be96f63375a1 ("powerpc: Split out instruction analysis part of > emulate_step()") > Signed-off-by: Ravi Bangoria <ravi.bango...@linux.vnet.ibm.com> > Reviewed-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com> > Reviewed-by: Ananth N Mavinakayanahalli <ana...@linux.vnet.ibm.com>
Applied to powerpc fixes, thanks. https://git.kernel.org/powerpc/c/9e1ba4f27f018742a1aa95d11e3510 cheers