[PATCH 5.4 069/154] ARM: 9350/1: fault: Implement copy_from_kernel_nofault_allowed()

[PATCH 5.4 069/154] ARM: 9350/1: fault: Implement copy_from_kernel_nofault_allowed()

[Greg Kroah-Hartman]

5.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@chromium.org>

commit 169f9102f9198b04afffa6164372a4ba4070f412 upstream.

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.

Closes: https://lava.sirena.org.uk/scheduler/job/497571
Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/ [1]

Reported-by: Mark Brown <broonie@kernel.org>
Suggested-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Cc: Wang Kefeng <wangkefeng.wang@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/arm/mm/fault.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- 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
 
 /*

[PATCH 5.4 070/154] ARM: 9351/1: fault: Add "cut here" line for prefetch aborts

[Greg Kroah-Hartman]

5.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@chromium.org>

commit 8f09b8b4fa58e99cbfd9a650b31d65cdbd8e4276 upstream.

The common pattern in arm is to emit a "8<--- cut here ---" line for
faults, but it was missing for do_PrefetchAbort(). Add it.

Cc: Wang Kefeng <wangkefeng.wang@huawei.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/arm/mm/fault.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -570,6 +570,7 @@ do_PrefetchAbort(unsigned long addr, uns
 	if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
 		return;
 
+	pr_alert("8<--- cut here ---\n");
 	pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
 		inf->name, ifsr, addr);