kernel.git/arch/x86/kernel/dumpstack.c, branch linux-4.19.y

x86/show_trace_log_lvl: Ensure stack pointer is aligned, again

2023-05-30T11:42:15Z

commit 2e4be0d011f21593c6b316806779ba1eba2cd7e0 upstream. The commit e335bb51cc15 ("x86/unwind: Ensure stack pointer is aligned") tried to align the stack pointer in show_trace_log_lvl(), otherwise the "stack < stack_info.end" check can't guarantee that the last read does not go past the end of the stack. However, we have the same problem with the initial value of the stack pointer, it can also be unaligned. So without this patch this trivial kernel module #include static int init(void) { asm volatile("sub $0x4,%rsp"); dump_stack(); asm volatile("add $0x4,%rsp"); return -EAGAIN; } module_init(init); MODULE_LICENSE("GPL"); crashes the kernel. Fixes: e335bb51cc15 ("x86/unwind: Ensure stack pointer is aligned") Signed-off-by: Vernon Lovejoy Signed-off-by: Oleg Nesterov Link: https://lore.kernel.org/r/20230512104232.GA10227@redhat.com Signed-off-by: Josh Poimboeuf Signed-off-by: Greg Kroah-Hartman

exit: Add and use make_task_dead.

2023-02-06T06:49:45Z

commit 0e25498f8cd43c1b5aa327f373dd094e9a006da7 upstream. There are two big uses of do_exit. The first is it's design use to be the guts of the exit(2) system call. The second use is to terminate a task after something catastrophic has happened like a NULL pointer in kernel code. Add a function make_task_dead that is initialy exactly the same as do_exit to cover the cases where do_exit is called to handle catastrophic failure. In time this can probably be reduced to just a light wrapper around do_task_dead. For now keep it exactly the same so that there will be no behavioral differences introducing this new concept. Replace all of the uses of do_exit that use it for catastraphic task cleanup with make_task_dead to make it clear what the code is doing. As part of this rename rewind_stack_do_exit rewind_stack_and_make_dead. Signed-off-by: "Eric W. Biederman" Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman

x86/process: Don't mix user/kernel regs in 64bit __show_regs()

2018-09-06T12:33:12Z

When the kernel.print-fatal-signals sysctl has been enabled, a simple userspace crash will cause the kernel to write a crash dump that contains, among other things, the kernel gsbase into dmesg. As suggested by Andy, limit output to pt_regs, FS_BASE and KERNEL_GS_BASE in this case. This also moves the bitness-specific logic from show_regs() into process_{32,64}.c. Fixes: 45807a1df9f5 ("vdso: print fatal signals") Signed-off-by: Jann Horn Signed-off-by: Thomas Gleixner Cc: "H. Peter Anvin" Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Greg Kroah-Hartman Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180831194151.123586-1-jannh@google.com

x86/dumpstack: Don't dump kernel memory based on usermode RIP

2018-08-31T15:08:22Z

show_opcodes() is used both for dumping kernel instructions and for dumping user instructions. If userspace causes #PF by jumping to a kernel address, show_opcodes() can be reached with regs->ip controlled by the user, pointing to kernel code. Make sure that userspace can't trick us into dumping kernel memory into dmesg. Fixes: 7cccf0725cf7 ("x86/dumpstack: Add a show_ip() function") Signed-off-by: Jann Horn Signed-off-by: Thomas Gleixner Reviewed-by: Kees Cook Reviewed-by: Borislav Petkov Cc: "H. Peter Anvin" Cc: Andy Lutomirski Cc: security@kernel.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180828154901.112726-1-jannh@google.com

x86/entry/64: Wipe KASAN stack shadow before rewind_stack_do_exit()

2018-08-30T09:37:09Z

Reset the KASAN shadow state of the task stack before rewinding RSP. Without this, a kernel oops will leave parts of the stack poisoned, and code running under do_exit() can trip over such poisoned regions and cause nonsensical false-positive KASAN reports about stack-out-of-bounds bugs. This does not wipe the exception stacks; if an oops happens on an exception stack, it might result in random KASAN false-positives from other tasks afterwards. This is probably relatively uninteresting, since if the kernel oopses on an exception stack, there are most likely bigger things to worry about. It'd be more interesting if vmapped stacks and KASAN were compatible, since then handle_stack_overflow() would oops from exception stack context. Fixes: 2deb4be28077 ("x86/dumpstack: When OOPSing, rewind the stack before do_exit()") Signed-off-by: Jann Horn Signed-off-by: Thomas Gleixner Acked-by: Andrey Ryabinin Cc: Andy Lutomirski Cc: Dmitry Vyukov Cc: Alexander Potapenko Cc: Kees Cook Cc: kasan-dev@googlegroups.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180828184033.93712-1-jannh@google.com

x86: Avoid pr_cont() in show_opcodes()

2018-07-19T14:46:23Z

If concurrent printk() messages are emitted, then pr_cont() is making it extremly hard to decode which part of the output belongs to what. See the convoluted example at: https://syzkaller.appspot.com/text?tag=CrashReport&x=139d342c400000 Avoid this by using a proper prefix for each line and by using %ph format in show_opcodes() which emits the 'Code:' line in one go. Signed-off-by: Rasmus Villemoes Signed-off-by: Tetsuo Handa Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: joe@perches.com Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Josh Poimboeuf Cc: Linus Torvalds Link: https://lkml.kernel.org/r/1532009278-5953-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp

x86/dumpstack: Explain the reasoning for the prologue and buffer size

2018-04-26T14:15:28Z

The whole reasoning behind the amount of opcode bytes dumped and prologue length isn't very clear so write down some of the reasons for why it is done the way it is. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Andy Lutomirski Link: https://lkml.kernel.org/r/20180417161124.5294-10-bp@alien8.de

x86/dumpstack: Save first regs set for the executive summary

2018-04-26T14:15:28Z

Save the regs set when __die() is onvoked for the first time and print it in oops_end(). Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Andy Lutomirski Link: https://lkml.kernel.org/r/20180417161124.5294-9-bp@alien8.de

x86/dumpstack: Add a show_ip() function

2018-04-26T14:15:27Z

... which shows the Instruction Pointer along with the insn bytes around it. Use it whenever rIP is printed. Drop the rIP < PAGE_OFFSET check since probe_kernel_read() can handle any address properly. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Andy Lutomirski Link: https://lkml.kernel.org/r/20180417161124.5294-8-bp@alien8.de

x86/dumpstack: Add loglevel argument to show_opcodes()

2018-04-26T14:15:26Z

Will be used in the next patch. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Andy Lutomirski Link: https://lkml.kernel.org/r/20180417161124.5294-6-bp@alien8.de