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arm64: poe: fix stale POR_EL0 values for ptrace

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If a process wrote to POR_EL0 and then crashed before a context switch
happened, the coredump would contain an incorrect value for POR_EL0.

The value read in poe_get() would be a stale value left in thread.por_el0.  Fix
this by reading the value from the system register, if the target thread is the
current thread.

This matches what gcs/fpsimd do.

Fixes: 1751981992 ("arm64/ptrace: add support for FEAT_POE")
Reported-by: David Spickett <david.spickett@arm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Joey Gouly 2026-01-27 13:39:26 +00:00 committed by Will Deacon
parent a4e5927115
commit 1f3b950492
1 changed files with 3 additions and 0 deletions
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3
arch/arm64/kernel/ptrace.c
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@ -1486,6 +1486,9 @@ static int poe_get(struct task_struct *target,
if (!system_supports_poe())
return -EINVAL;
if (target == current)
current->thread.por_el0 = read_sysreg_s(SYS_POR_EL0);
return membuf_write(&to, &target->thread.por_el0,
sizeof(target->thread.por_el0));
}