Re: [Xen-devel] [PATCH v2] Coverity ID: 1215178

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 22/05/14 16:06, Paul Durrant wrote:
> There are two problems with initializetion of the ioreq_t in hvmemul_do_io():
>
> - vp_eport is uninitialized (because it doesn't need to be) but because the
>   struct is the subject of a copy in hvm_send_assist_req(), this is flagged
>   as a problem.
> - dir, addr, data_is_ptr, and data may be uninitialized when the struct is
>   passed to hvmtrace_io_assist(). This is clearly a bug, so the initializ-
>   ation of at least those fields needs to be moved earlier.
>
> This patch fixes both these problems.
>
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Cc: Keir Fraser <keir@xxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

> ---
>  xen/arch/x86/hvm/emulate.c |   29 ++++++++++++++---------------
>  1 file changed, 14 insertions(+), 15 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
> index 904c71a..eac159f 100644
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -53,11 +53,17 @@ static int hvmemul_do_io(
>      int is_mmio, paddr_t addr, unsigned long *reps, int size,
>      paddr_t ram_gpa, int dir, int df, void *p_data)
>  {
> -    paddr_t value = ram_gpa;
> -    int value_is_ptr = (p_data == NULL);
>      struct vcpu *curr = current;
>      struct hvm_vcpu_io *vio;
> -    ioreq_t p;
> +    ioreq_t p = {
> +        .type = is_mmio ? IOREQ_TYPE_COPY : IOREQ_TYPE_PIO,
> +        .addr = addr,
> +        .size = size,
> +        .dir = dir,
> +        .df = df,
> +        .data = ram_gpa,
> +        .data_is_ptr = (p_data == NULL),
> +    };
>      unsigned long ram_gfn = paddr_to_pfn(ram_gpa);
>      p2m_type_t p2mt;
>      struct page_info *ram_page;
> @@ -94,15 +100,15 @@ static int hvmemul_do_io(
>          return X86EMUL_UNHANDLEABLE;
>      }
>  
> -    if ( (p_data != NULL) && (dir == IOREQ_WRITE) )
> +    if ( !p.data_is_ptr && (dir == IOREQ_WRITE) )
>      {
> -        memcpy(&value, p_data, size);
> +        memcpy(&p.data, p_data, size);
>          p_data = NULL;
>      }
>  
>      vio = &curr->arch.hvm_vcpu.hvm_io;
>  
> -    if ( is_mmio && !value_is_ptr )
> +    if ( is_mmio && !p.data_is_ptr )
>      {
>          /* Part of a multi-cycle read or write? */
>          if ( dir == IOREQ_WRITE )
> @@ -146,7 +152,7 @@ static int hvmemul_do_io(
>          goto finish_access;
>      case HVMIO_dispatched:
>          /* May have to wait for previous cycle of a multi-write to complete. 
> */
> -        if ( is_mmio && !value_is_ptr && (dir == IOREQ_WRITE) &&
> +        if ( is_mmio && !p.data_is_ptr && (dir == IOREQ_WRITE) &&
>               (addr == (vio->mmio_large_write_pa +
>                         vio->mmio_large_write_bytes)) )
>          {
> @@ -179,14 +185,7 @@ static int hvmemul_do_io(
>      if ( vio->mmio_retrying )
>          *reps = 1;
>  
> -    p.dir = dir;
> -    p.data_is_ptr = value_is_ptr;
> -    p.type = is_mmio ? IOREQ_TYPE_COPY : IOREQ_TYPE_PIO;
> -    p.size = size;
> -    p.addr = addr;
>      p.count = *reps;
> -    p.df = df;
> -    p.data = value;
>  
>      if ( dir == IOREQ_WRITE )
>          hvmtrace_io_assist(is_mmio, &p);
> @@ -251,7 +250,7 @@ static int hvmemul_do_io(
>      if ( p_data != NULL )
>          memcpy(p_data, &vio->io_data, size);
>  
> -    if ( is_mmio && !value_is_ptr )
> +    if ( is_mmio && !p.data_is_ptr )
>      {
>          /* Part of a multi-cycle read or write? */
>          if ( dir == IOREQ_WRITE )


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