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Fix race condition in HlComPortReadLsr

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The static local variable RingFlag in HlComPortReadLsr caused shared state across multiple calls and ports, leading to race conditions and incorrect behavior.
This commit is contained in:
Aiken Harris
2025-08-06 09:01:47 +02:00
committed by CodingWorkshop Signing Team
parent 9badf36ce0
commit d7552f1dce
1 changed files with 3 additions and 3 deletions
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6
xtoskrnl/hl/cport.c
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@@ -165,7 +165,6 @@ HlComPortReadLsr(IN PCPPORT Port,
IN UCHAR Byte)
{
UCHAR Lsr, Msr;
STATIC UCHAR RingFlag;
/* Read the Line Status Register (LSR) */
Lsr = HlIoPortInByte(PtrToUshort(Port->Address + (ULONG)COMPORT_REG_LSR));
@@ -175,8 +174,8 @@ HlComPortReadLsr(IN PCPPORT Port,
{
/* Check Modem Status Register (MSR) for ring indicator */
Msr = HlIoPortInByte(PtrToUshort(Port->Address + (ULONG)COMPORT_REG_MSR));
RingFlag |= (Msr & COMPORT_MSR_RI) ? 1 : 2;
if(RingFlag == 3)
Port->Ring |= (Msr & COMPORT_MSR_RI) ? 1 : 2;
if(Port->Ring == 3)
{
/* Ring indicator toggled, use modem control */
Port->Flags |= COMPORT_FLAG_MC;
@@ -283,6 +282,7 @@ HlInitializeComPort(IN OUT PCPPORT Port,
Port->Address = PortAddress;
Port->Baud = BaudRate;
Port->Flags = Flags;
Port->Ring = 0;
/* Return success */
return STATUS_SUCCESS;