mainlining shenanigans
97f88a3d72
I found a null pointer reference in arch_prepare_kprobe():
# echo 'p cmdline_proc_show' > kprobe_events
# echo 'p cmdline_proc_show+16' >> kprobe_events
Kernel attempted to read user page (0) - exploit attempt? (uid: 0)
BUG: Kernel NULL pointer dereference on read at 0x00000000
Faulting instruction address: 0xc000000000050bfc
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA PowerNV
Modules linked in:
CPU: 0 PID: 122 Comm: sh Not tainted 6.0.0-rc3-00007-gdcf8e5633e2e #10
NIP: c000000000050bfc LR: c000000000050bec CTR: 0000000000005bdc
REGS: c0000000348475b0 TRAP: 0300 Not tainted (6.0.0-rc3-00007-gdcf8e5633e2e)
MSR: 9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 88002444 XER: 20040006
CFAR: c00000000022d100 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0
...
NIP arch_prepare_kprobe+0x10c/0x2d0
LR arch_prepare_kprobe+0xfc/0x2d0
Call Trace:
0xc0000000012f77a0 (unreliable)
register_kprobe+0x3c0/0x7a0
__register_trace_kprobe+0x140/0x1a0
__trace_kprobe_create+0x794/0x1040
trace_probe_create+0xc4/0xe0
create_or_delete_trace_kprobe+0x2c/0x80
trace_parse_run_command+0xf0/0x210
probes_write+0x20/0x40
vfs_write+0xfc/0x450
ksys_write+0x84/0x140
system_call_exception+0x17c/0x3a0
system_call_vectored_common+0xe8/0x278
--- interrupt: 3000 at 0x7fffa5682de0
NIP: 00007fffa5682de0 LR: 0000000000000000 CTR: 0000000000000000
REGS: c000000034847e80 TRAP: 3000 Not tainted (6.0.0-rc3-00007-gdcf8e5633e2e)
MSR: 900000000280f033 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 44002408 XER: 00000000
The address being probed has some special:
cmdline_proc_show: Probe based on ftrace
cmdline_proc_show+16: Probe for the next instruction at the ftrace location
The ftrace-based kprobe does not generate kprobe::ainsn::insn, it gets
set to NULL. In arch_prepare_kprobe() it will check for:
...
prev = get_kprobe(p->addr - 1);
preempt_enable_no_resched();
if (prev && ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) {
...
If prev is based on ftrace, 'ppc_inst_read(prev->ainsn.insn)' will occur
with a null pointer reference. At this point prev->addr will not be a
prefixed instruction, so the check can be skipped.
Check if prev is ftrace-based kprobe before reading 'prev->ainsn.insn'
to fix this problem.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.