Under PAN emulation when dumping backtraces from things like the
LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU)
would happen because of dump_instr() attempting to read a userspace
address. Make sure copy_from_kernel_nofault() does not attempt this
any more.
Reported-by: Mark Brown <[email protected]>
Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/ [1]
Suggested-by: "Russell King (Oracle)" <[email protected]>
Cc: Russell King <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Wang Kefeng <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Ben Hutchings <[email protected]>
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
---
arch/arm/mm/fault.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index e804432e905e..bc5b959b6f90 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -25,6 +25,13 @@
#include "fault.h"
+bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
+{
+ unsigned long addr = (unsigned long)unsafe_src;
+
+ return addr >= TASK_SIZE && ULONG_MAX - addr >= size;
+}
+
#ifdef CONFIG_MMU
/*
--
2.34.1
On Tue, 23 Jan 2024 at 02:12, Kees Cook <[email protected]> wrote:
>
> Under PAN emulation when dumping backtraces from things like the
> LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU)
> would happen because of dump_instr() attempting to read a userspace
> address. Make sure copy_from_kernel_nofault() does not attempt this
> any more.
>
> Reported-by: Mark Brown <[email protected]>
> Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/ [1]
> Suggested-by: "Russell King (Oracle)" <[email protected]>
> Cc: Russell King <[email protected]>
> Cc: Ard Biesheuvel <[email protected]>
> Cc: Wang Kefeng <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Ben Hutchings <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
> ---
> arch/arm/mm/fault.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
> index e804432e905e..bc5b959b6f90 100644
> --- a/arch/arm/mm/fault.c
> +++ b/arch/arm/mm/fault.c
> @@ -25,6 +25,13 @@
>
> #include "fault.h"
>
> +bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
> +{
> + unsigned long addr = (unsigned long)unsafe_src;
> +
> + return addr >= TASK_SIZE && ULONG_MAX - addr >= size;
> +}
> +
> #ifdef CONFIG_MMU
>
> /*
> --
> 2.34.1
>
On Mon, Jan 22, 2024 at 05:12:38PM -0800, Kees Cook wrote:
> Under PAN emulation when dumping backtraces from things like the
> LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU)
> would happen because of dump_instr() attempting to read a userspace
> address. Make sure copy_from_kernel_nofault() does not attempt this
> any more.
This appears to fix the original issue:
https://lava.sirena.org.uk/scheduler/job/497571
(though so did your earlier patch) so:
Tested-by: Mark Brown <[email protected]>
On Mon, Jan 22, 2024 at 05:12:38PM -0800, Kees Cook wrote:
> Under PAN emulation when dumping backtraces from things like the
> LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU)
> would happen because of dump_instr() attempting to read a userspace
> address. Make sure copy_from_kernel_nofault() does not attempt this
> any more.
>
> Reported-by: Mark Brown <[email protected]>
> Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/ [1]
> Suggested-by: "Russell King (Oracle)" <[email protected]>
> Cc: Russell King <[email protected]>
> Cc: Ard Biesheuvel <[email protected]>
> Cc: Wang Kefeng <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Ben Hutchings <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>
Russell, do you mind if I carry in my tree the 3 ARM patches I sent?
They're mostly pretty trivial, and they've been in "Incoming"[1] for 2
weeks but haven't shown up in -next yet. I'd really like them to get
some soak time, and for them to reach the v6.9 merge window in time.
Please let me know what you think. :) Thanks!
-Kees
[1] https://www.arm.linux.org.uk/developer/patches/section.php?section=0
--
Kees Cook
On Tue, Feb 20, 2024 at 10:39:15PM -0800, Kees Cook wrote:
> On Mon, Jan 22, 2024 at 05:12:38PM -0800, Kees Cook wrote:
> > Under PAN emulation when dumping backtraces from things like the
> > LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU)
> > would happen because of dump_instr() attempting to read a userspace
> > address. Make sure copy_from_kernel_nofault() does not attempt this
> > any more.
> >
> > Reported-by: Mark Brown <[email protected]>
> > Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/ [1]
> > Suggested-by: "Russell King (Oracle)" <[email protected]>
> > Cc: Russell King <[email protected]>
> > Cc: Ard Biesheuvel <[email protected]>
> > Cc: Wang Kefeng <[email protected]>
> > Cc: Andrew Morton <[email protected]>
> > Cc: Ben Hutchings <[email protected]>
> > Cc: [email protected]
> > Signed-off-by: Kees Cook <[email protected]>
>
> Russell, do you mind if I carry in my tree the 3 ARM patches I sent?
> They're mostly pretty trivial, and they've been in "Incoming"[1] for 2
> weeks but haven't shown up in -next yet. I'd really like them to get
> some soak time, and for them to reach the v6.9 merge window in time.
They can't show up in -next at the moment because the machine that hosts
my git tree is being moved between data centres. This was originally
flagged as a same-day (Tuesday) move, then next day, then it'll be back
online on Saturday. That's the last update that we've had.
As I don't believe my GPG key has the necessary signatures on, I don't
believe I can get a kernel.org account. I'm not even sure whether my
gpg key is even correct for that - and at the moment I just glaze over
reading the kernel.org gpg documentation.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
On Wed, Feb 21, 2024 at 11:29:38AM +0000, Russell King (Oracle) wrote:
> On Tue, Feb 20, 2024 at 10:39:15PM -0800, Kees Cook wrote:
> > On Mon, Jan 22, 2024 at 05:12:38PM -0800, Kees Cook wrote:
> > > Under PAN emulation when dumping backtraces from things like the
> > > LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU)
> > > would happen because of dump_instr() attempting to read a userspace
> > > address. Make sure copy_from_kernel_nofault() does not attempt this
> > > any more.
> > >
> > > Reported-by: Mark Brown <[email protected]>
> > > Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/ [1]
> > > Suggested-by: "Russell King (Oracle)" <[email protected]>
> > > Cc: Russell King <[email protected]>
> > > Cc: Ard Biesheuvel <[email protected]>
> > > Cc: Wang Kefeng <[email protected]>
> > > Cc: Andrew Morton <[email protected]>
> > > Cc: Ben Hutchings <[email protected]>
> > > Cc: [email protected]
> > > Signed-off-by: Kees Cook <[email protected]>
> >
> > Russell, do you mind if I carry in my tree the 3 ARM patches I sent?
> > They're mostly pretty trivial, and they've been in "Incoming"[1] for 2
> > weeks but haven't shown up in -next yet. I'd really like them to get
> > some soak time, and for them to reach the v6.9 merge window in time.
>
> They can't show up in -next at the moment because the machine that hosts
> my git tree is being moved between data centres. This was originally
> flagged as a same-day (Tuesday) move, then next day, then it'll be back
> online on Saturday. That's the last update that we've had.
>
> As I don't believe my GPG key has the necessary signatures on, I don't
> believe I can get a kernel.org account. I'm not even sure whether my
> gpg key is even correct for that - and at the moment I just glaze over
> reading the kernel.org gpg documentation.
I'll also point out that over the last two weeks, the first week I was
in Cambridge attending a conference at Arm Ltd, and then I went down
with full blown flu shortly there-after.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!