Re: 答复: [RFC v4 5/6] UefiCpuPkg/CpuExceptionHandlerLib: Ensure valid frame/stack pointers

[Paulo Alcantara <paulo@paulo.ac>]

On 1/3/2018 6:45 AM, Fan Jeff wrote:
> Paulo,
> 
> +    if (!IsLogicalAddressValid (SystemContext,
> +                                SystemContext.SystemContextIa32->Ss,
> +                                (UINTN)Ebp) ||
> +        !IsLogicalAddressValid (SystemContext,
> +                                SystemContext.SystemContextIa32->Ss,
> +                                (UINTN)Ebp + 4)) {
> 
> I don’t understand why you check both ebp and ebp+4, I think it’s enough 
> to only check EBP (saved stack pointer address)

Isn't it possible that EBP + 4 might potentially point to another page 
frame? If not, then I will drop it out in v5.

Thanks
Paulo

> 
> Jeff
> 
> *发件人: *Paulo Alcantara <mailto:paulo@paulo.ac>
> *发送时间: *2017年12月29日12:41
> *收件人: *edk2-devel@lists.01.org <mailto:edk2-devel@lists.01.org>
> *抄送: *Laszlo Ersek <mailto:lersek@redhat.com>; Eric Dong 
> <mailto:eric.dong@intel.com>
> *主题: *[edk2] [RFC v4 5/6] UefiCpuPkg/CpuExceptionHandlerLib: Ensure 
> valid frame/stack pointers
> 
> Validate all possible memory dereferences during stack traces in IA32
> and X64 CPU exceptions.
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Requested-by: Brian Johnson <brian.johnson@hpe.com>
> Requested-by: Jiewen Yao <jiewen.yao@intel.com>
> Signed-off-by: Paulo Alcantara <paulo@paulo.ac>
> ---
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.c 
> | 143 +++++++++++++++++++-
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c  
> |  75 +++++++++-
>   2 files changed, 210 insertions(+), 8 deletions(-)
> 
> diff --git 
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.c 
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.c
> index 25e02fbbc1..9b52d4f6d2 100644
> --- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.c
> +++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ArchExceptionHandler.c
> @@ -398,6 +398,96 @@ DumpCpuContext (
>       );
>   }
> 
> +/**
> +  Check if a logical address is valid.
> +
> +  @param[in]  SystemContext      Pointer to EFI_SYSTEM_CONTEXT.
> +  @param[in]  SegmentSelector    Segment selector.
> +  @param[in]  Offset             Offset or logical address.
> +**/
> +STATIC
> +BOOLEAN
> +IsLogicalAddressValid (
> +  IN  EFI_SYSTEM_CONTEXT   SystemContext,
> +  IN  UINT16               SegmentSelector,
> +  IN  UINTN                Offset
> +  )
> +{
> +  IA32_SEGMENT_DESCRIPTOR  *SegmentDescriptor;
> +  UINT32                   SegDescBase;
> +  UINT32                   SegDescLimit;
> +  UINTN                    SegDescLimitInBytes;
> +
> +  //
> +  // Check for valid input parameters
> +  //
> +  if (SegmentSelector == 0 || Offset == 0) {
> +    return FALSE;
> +  }
> +
> +  //
> +  // Check whether to look for a segment descriptor in GDT or LDT table
> +  //
> +  if ((SegmentSelector & BIT2) == 0) {
> +    //
> +    // Get segment descriptor from GDT table
> +    //
> +    SegmentDescriptor =
> +      (IA32_SEGMENT_DESCRIPTOR *)(
> +        (UINTN)SystemContext.SystemContextIa32->Gdtr[0] +
> +        ((SegmentSelector >> 3) * 8)
> +        );
> +  } else {
> +    //
> +    // Get segment descriptor from LDT table
> +    //
> +    SegmentDescriptor =
> +      (IA32_SEGMENT_DESCRIPTOR *)(
> +        (UINTN)SystemContext.SystemContextIa32->Ldtr +
> +        ((SegmentSelector >> 3) * 8)
> +        );
> +  }
> +
> +  //
> +  // Get segment descriptor's base address
> +  //
> +  SegDescBase = SegmentDescriptor->Bits.BaseLow |
> +    (SegmentDescriptor->Bits.BaseMid << 16) |
> +    (SegmentDescriptor->Bits.BaseHigh << 24);
> +
> +  //
> +  // Get segment descriptor's limit
> +  //
> +  SegDescLimit = SegmentDescriptor->Bits.LimitLow |
> +    (SegmentDescriptor->Bits.LimitHigh << 16);
> +
> +  //
> +  // Calculate segment descriptor's limit in bytes
> +  //
> +  if (SegmentDescriptor->Bits.G == 1) {
> +    SegDescLimitInBytes = (UINTN)SegDescLimit * SIZE_4KB;
> +  } else {
> +    SegDescLimitInBytes = SegDescLimit;
> +  }
> +
> +  //
> +  // Make sure to not access beyond a segment limit boundary
> +  //
> +  if (Offset + SegDescBase > SegDescLimitInBytes) {
> +    return FALSE;
> +  }
> +
> +  //
> +  // Check if the translated logical address (or linear address) is valid
> +  //
> +  return IsLinearAddressValid (
> +    SystemContext.SystemContextIa32->Cr0,
> +    SystemContext.SystemContextIa32->Cr3,
> +    SystemContext.SystemContextIa32->Cr4,
> +    Offset + SegDescBase
> +    );
> +}
> +
>   /**
>     Dump stack trace.
> 
> @@ -459,6 +549,20 @@ DumpStackTrace (
>     InternalPrintMessage ("\nCall trace:\n");
> 
>     for (;;) {
> +    //
> +    // Check for valid frame pointer
> +    //
> +    if (!IsLogicalAddressValid (SystemContext,
> +                                SystemContext.SystemContextIa32->Ss,
> +                                (UINTN)Ebp + 4) ||
> +        !IsLogicalAddressValid (SystemContext,
> +                                SystemContext.SystemContextIa32->Ss,
> +                                (UINTN)Ebp)) {
> +      InternalPrintMessage ("%a: attempted to dereference an invalid 
> frame "
> +                            "pointer at 0x%08x\n", __FUNCTION__, Ebp);
> +      break;
> +    }
> +
>       //
>       // Print stack frame in the following format:
>       //
> @@ -588,6 +692,16 @@ DumpImageModuleNames (
>     // Walk through call stack and find next module names
>     //
>     for (;;) {
> +    if (!IsLogicalAddressValid (SystemContext,
> +                                SystemContext.SystemContextIa32->Ss,
> +                                (UINTN)Ebp) ||
> +        !IsLogicalAddressValid (SystemContext,
> +                                SystemContext.SystemContextIa32->Ss,
> +                                (UINTN)Ebp + 4)) {
> +      InternalPrintMessage ("%a: attempted to dereference an invalid 
> frame "
> +                            "pointer at 0x%08x\n", __FUNCTION__, Ebp);
> +    }
> +
>       //
>       // Set EIP with return address from current stack frame
>       //
> @@ -651,16 +765,23 @@ DumpImageModuleNames (
>   /**
>     Dump stack contents.
> 
> -  @param[in]  CurrentEsp         Current stack pointer address.
> +  @param[in]  SystemContext       Pointer to EFI_SYSTEM_CONTEXT.
>     @param[in]  UnwoundStacksCount  Count of unwound stack frames.
>   **/
>   STATIC
>   VOID
>   DumpStackContents (
> -  IN UINT32  CurrentEsp,
> -  IN INTN    UnwoundStacksCount
> +  IN  EFI_SYSTEM_CONTEXT  SystemContext,
> +  IN  INTN                UnwoundStacksCount
>     )
>   {
> +  UINT32 CurrentEsp;
> +
> +  //
> +  // Get current stack pointer
> +  //
> +  CurrentEsp = SystemContext.SystemContextIa32->Esp;
> +
>     //
>     // Check for proper stack alignment
>     //
> @@ -674,6 +795,20 @@ DumpStackContents (
>     //
>     InternalPrintMessage ("\nStack dump:\n");
>     while (UnwoundStacksCount-- > 0) {
> +    //
> +    // Check for a valid stack pointer address
> +    //
> +    if (!IsLogicalAddressValid (SystemContext,
> +                                SystemContext.SystemContextIa32->Ss,
> +                                (UINTN)CurrentEsp) ||
> +        !IsLogicalAddressValid (SystemContext,
> +                                SystemContext.SystemContextIa32->Ss,
> +                                (UINTN)CurrentEsp + 4)) {
> +      InternalPrintMessage ("%a: attempted to dereference an invalid 
> stack "
> +                            "pointer at 0x%08x\n", __FUNCTION__, 
> CurrentEsp);
> +      break;
> +    }
> +
>       InternalPrintMessage (
>         "0x%08x: %08x %08x\n",
>         CurrentEsp,
> @@ -720,5 +855,5 @@ DumpImageAndCpuContent (
>     //
>     // Dump stack contents
>     //
> -  DumpStackContents (SystemContext.SystemContextIa32->Esp, 
> UnwoundStacksCount);
> +  DumpStackContents (SystemContext, UnwoundStacksCount);
>   }
> diff --git 
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c 
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
> index d3a3878b3d..8067c34122 100644
> --- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
> +++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ArchExceptionHandler.c
> @@ -401,16 +401,26 @@ DumpCpuContext (
>   /**
>     Dump stack contents.
> 
> -  @param[in]  CurrentRsp         Current stack pointer address.
> +  @param[in]  SystemContext       Pointer to EFI_SYSTEM_CONTEXT.
>     @param[in]  UnwoundStacksCount  Count of unwound stack frames.
>   **/
>   STATIC
>   VOID
>   DumpStackContents (
> -  IN UINT64  CurrentRsp,
> -  IN INTN    UnwoundStacksCount
> +  IN  EFI_SYSTEM_CONTEXT  SystemContext,
> +  IN  INTN                UnwoundStacksCount
>     )
>   {
> +  UINT64  CurrentRsp;
> +  UINTN   Cr0;
> +  UINTN   Cr3;
> +  UINTN   Cr4;
> +
> +  //
> +  // Get current stack pointer
> +  //
> +  CurrentRsp = SystemContext.SystemContextX64->Rsp;
> +
>     //
>     // Check for proper stack pointer alignment
>     //
> @@ -419,11 +429,28 @@ DumpStackContents (
>       return;
>     }
> 
> +  //
> +  // Get system control registers
> +  //
> +  Cr0 = SystemContext.SystemContextX64->Cr0;
> +  Cr3 = SystemContext.SystemContextX64->Cr3;
> +  Cr4 = SystemContext.SystemContextX64->Cr4;
> +
>     //
>     // Dump out stack contents
>     //
>     InternalPrintMessage ("\nStack dump:\n");
>     while (UnwoundStacksCount-- > 0) {
> +    //
> +    // Check for a valid stack pointer address
> +    //
> +    if (!IsLinearAddressValid (Cr0, Cr3, Cr4, (UINTN)CurrentRsp) ||
> +        !IsLinearAddressValid (Cr0, Cr3, Cr4, (UINTN)CurrentRsp + 8)) {
> +      InternalPrintMessage ("%a: attempted to dereference an invalid 
> stack "
> +                            "pointer at 0x%016lx\n", __FUNCTION__, 
> CurrentRsp);
> +      break;
> +    }
> +
>       InternalPrintMessage (
>         "0x%016lx: %016lx %016lx\n",
>         CurrentRsp,
> @@ -457,6 +484,9 @@ DumpImageModuleNames (
>     CHAR8       *PdbFileName;
>     UINT64      Rbp;
>     UINTN       LastImageBase;
> +  UINTN       Cr0;
> +  UINTN       Cr3;
> +  UINTN       Cr4;
> 
>     //
>     // Set current RIP address
> @@ -516,10 +546,27 @@ DumpImageModuleNames (
>       InternalPrintMessage ("%a\n", PdbAbsoluteFilePath);
>     }
> 
> +  //
> +  // Get system control registers
> +  //
> +  Cr0 = SystemContext.SystemContextX64->Cr0;
> +  Cr3 = SystemContext.SystemContextX64->Cr3;
> +  Cr4 = SystemContext.SystemContextX64->Cr4;
> +
>     //
>     // Walk through call stack and find next module names
>     //
>     for (;;) {
> +    //
> +    // Check for a valid frame pointer
> +    //
> +    if (!IsLinearAddressValid (Cr0, Cr3, Cr4, (UINTN)Rbp + 8) ||
> +        !IsLinearAddressValid (Cr0, Cr3, Cr4, (UINTN)Rbp)) {
> +      InternalPrintMessage ("%a: attempted to dereference an invalid 
> frame "
> +                            "pointer at 0x%016lx\n", __FUNCTION__, Rbp);
> +      break;
> +    }
> +
>       //
>       // Set RIP with return address from current stack frame
>       //
> @@ -604,6 +651,9 @@ DumpStackTrace (
>     UINT64  Rbp;
>     UINTN   ImageBase;
>     CHAR8   *PdbFileName;
> +  UINTN   Cr0;
> +  UINTN   Cr3;
> +  UINTN   Cr4;
> 
>     //
>     // Set current RIP address
> @@ -634,12 +684,29 @@ DumpStackTrace (
>     //
>     *UnwoundStacksCount = 1;
> 
> +  //
> +  // Get system control registers
> +  //
> +  Cr0 = SystemContext.SystemContextX64->Cr0;
> +  Cr3 = SystemContext.SystemContextX64->Cr3;
> +  Cr4 = SystemContext.SystemContextX64->Cr4;
> +
>     //
>     // Print out back trace
>     //
>     InternalPrintMessage ("\nCall trace:\n");
> 
>     for (;;) {
> +    //
> +    // Check for valid frame pointer
> +    //
> +    if (!IsLinearAddressValid (Cr0, Cr3, Cr4, (UINTN)Rbp + 8) ||
> +        !IsLinearAddressValid (Cr0, Cr3, Cr4, (UINTN)Rbp)) {
> +      InternalPrintMessage ("%a: attempted to dereference an invalid 
> frame "
> +                            "pointer at 0x%016lx\n", __FUNCTION__, Rbp);
> +      break;
> +    }
> +
>       //
>       // Print stack frame in the following format:
>       //
> @@ -727,5 +794,5 @@ DumpImageAndCpuContent (
>     //
>     // Dump stack contents
>     //
> -  DumpStackContents (SystemContext.SystemContextX64->Rsp, 
> UnwoundStacksCount);
> +  DumpStackContents (SystemContext, UnwoundStacksCount);
>   }
> -- 
> 2.14.3
> 
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