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ARM: 9350/1: fault: Implement copy_from_kernel_nofault_allowed()

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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>
This commit is contained in:
Kees Cook 2024-02-01 18:32:58 +01:00 committed by Russell King (Oracle)
parent daa559570d
commit 169f9102f9
1 changed files with 7 additions and 0 deletions
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7
arch/arm/mm/fault.c
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@ -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
/*