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[PATCH-for-5.1] hw/ide/ahci: Do not dma_memory_unmap(NULL)

Philippe Mathieu-Daudé posted 1 patch 5 years, 4 months ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/20200718072854.7001-1-f4bug@amsat.org
hw/ide/ahci.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
[PATCH-for-5.1] hw/ide/ahci: Do not dma_memory_unmap(NULL)
Posted by Philippe Mathieu-Daudé 5 years, 4 months ago 
libFuzzer triggered the following assertion:

  cat << EOF | qemu-system-i386 -M pc-q35-5.0 \
    -nographic -monitor none -serial none -qtest stdio
  outl 0xcf8 0x8000fa24
  outl 0xcfc 0xe1068000
  outl 0xcf8 0x8000fa04
  outw 0xcfc 0x7
  outl 0xcf8 0x8000fb20
  write 0xe1068304 0x1 0x21
  write 0xe1068318 0x1 0x21
  write 0xe1068384 0x1 0x21
  write 0xe1068398 0x2 0x21
  EOF
  qemu-system-i386: exec.c:3621: address_space_unmap: Assertion `mr != NULL' failed.
  Aborted (core dumped)

This is because we don't check the return value from dma_memory_map()
which can return NULL, then we call dma_memory_unmap(NULL) which is
illegal. Fix by only unmap if the value is not NULL (and the size is
not the expected one).

Cc: qemu-stable@nongnu.org
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Fixes: f6ad2e32f8 ("ahci: add ahci emulation")
BugLink: https://bugs.launchpad.net/qemu/+bug/1884693
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/ide/ahci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index 009120f88b..4f596cb9ce 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -250,7 +250,7 @@ static void map_page(AddressSpace *as, uint8_t **ptr, uint64_t addr,
     }
 
     *ptr = dma_memory_map(as, addr, &len, DMA_DIRECTION_FROM_DEVICE);
-    if (len < wanted) {
+    if (len < wanted && *ptr) {
         dma_memory_unmap(as, *ptr, len, DMA_DIRECTION_FROM_DEVICE, len);
         *ptr = NULL;
     }
-- 
2.21.3
Re: [PATCH-for-5.1] hw/ide/ahci: Do not dma_memory_unmap(NULL)
Posted by Philippe Mathieu-Daudé 5 years, 3 months ago 
On 7/18/20 9:28 AM, Philippe Mathieu-Daudé wrote:
> libFuzzer triggered the following assertion:
> 
>   cat << EOF | qemu-system-i386 -M pc-q35-5.0 \
>     -nographic -monitor none -serial none -qtest stdio
>   outl 0xcf8 0x8000fa24
>   outl 0xcfc 0xe1068000
>   outl 0xcf8 0x8000fa04
>   outw 0xcfc 0x7
>   outl 0xcf8 0x8000fb20
>   write 0xe1068304 0x1 0x21
>   write 0xe1068318 0x1 0x21
>   write 0xe1068384 0x1 0x21
>   write 0xe1068398 0x2 0x21
>   EOF
>   qemu-system-i386: exec.c:3621: address_space_unmap: Assertion `mr != NULL' failed.
>   Aborted (core dumped)
> 
> This is because we don't check the return value from dma_memory_map()
> which can return NULL, then we call dma_memory_unmap(NULL) which is
> illegal. Fix by only unmap if the value is not NULL (and the size is
> not the expected one).

Maybe worth mentioning it was hidden before but got revealed by commit
77f55eac6c ("exec: set map length to zero when returning NULL").

Cc'ing commit 77f55eac6c's reviewers.

> Cc: qemu-stable@nongnu.org
> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> Fixes: f6ad2e32f8 ("ahci: add ahci emulation")
> BugLink: https://bugs.launchpad.net/qemu/+bug/1884693
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  hw/ide/ahci.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
> index 009120f88b..4f596cb9ce 100644
> --- a/hw/ide/ahci.c
> +++ b/hw/ide/ahci.c
> @@ -250,7 +250,7 @@ static void map_page(AddressSpace *as, uint8_t **ptr, uint64_t addr,
>      }
>  
>      *ptr = dma_memory_map(as, addr, &len, DMA_DIRECTION_FROM_DEVICE);
> -    if (len < wanted) {
> +    if (len < wanted && *ptr) {
>          dma_memory_unmap(as, *ptr, len, DMA_DIRECTION_FROM_DEVICE, len);
>          *ptr = NULL;
>      }
>
Re: [PATCH-for-5.1] hw/ide/ahci: Do not dma_memory_unmap(NULL)
Posted by John Snow 5 years, 3 months ago 
On 7/18/20 3:28 AM, Philippe Mathieu-Daudé wrote:
> libFuzzer triggered the following assertion:
> 
>    cat << EOF | qemu-system-i386 -M pc-q35-5.0 \
>      -nographic -monitor none -serial none -qtest stdio
>    outl 0xcf8 0x8000fa24
>    outl 0xcfc 0xe1068000
>    outl 0xcf8 0x8000fa04
>    outw 0xcfc 0x7
>    outl 0xcf8 0x8000fb20
>    write 0xe1068304 0x1 0x21
>    write 0xe1068318 0x1 0x21
>    write 0xe1068384 0x1 0x21
>    write 0xe1068398 0x2 0x21
>    EOF
>    qemu-system-i386: exec.c:3621: address_space_unmap: Assertion `mr != NULL' failed.
>    Aborted (core dumped)
> 
> This is because we don't check the return value from dma_memory_map()
> which can return NULL, then we call dma_memory_unmap(NULL) which is
> illegal. Fix by only unmap if the value is not NULL (and the size is
> not the expected one).
> 
> Cc: qemu-stable@nongnu.org
> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> Fixes: f6ad2e32f8 ("ahci: add ahci emulation")
> BugLink: https://bugs.launchpad.net/qemu/+bug/1884693
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>   hw/ide/ahci.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
> index 009120f88b..4f596cb9ce 100644
> --- a/hw/ide/ahci.c
> +++ b/hw/ide/ahci.c
> @@ -250,7 +250,7 @@ static void map_page(AddressSpace *as, uint8_t **ptr, uint64_t addr,
>       }
>   
>       *ptr = dma_memory_map(as, addr, &len, DMA_DIRECTION_FROM_DEVICE);
> -    if (len < wanted) {
> +    if (len < wanted && *ptr) {
>           dma_memory_unmap(as, *ptr, len, DMA_DIRECTION_FROM_DEVICE, len);
>           *ptr = NULL;
>       }
> 

Reviewed-by: John Snow <jsnow@redhat.com>

Thanks! this one wound up being easy.
Re: [PATCH-for-5.1] hw/ide/ahci: Do not dma_memory_unmap(NULL)
Posted by John Snow 5 years, 3 months ago 
On 7/18/20 3:28 AM, Philippe Mathieu-Daudé wrote:
> libFuzzer triggered the following assertion:
> 
>    cat << EOF | qemu-system-i386 -M pc-q35-5.0 \
>      -nographic -monitor none -serial none -qtest stdio
>    outl 0xcf8 0x8000fa24
>    outl 0xcfc 0xe1068000
>    outl 0xcf8 0x8000fa04
>    outw 0xcfc 0x7
>    outl 0xcf8 0x8000fb20
>    write 0xe1068304 0x1 0x21
>    write 0xe1068318 0x1 0x21
>    write 0xe1068384 0x1 0x21
>    write 0xe1068398 0x2 0x21
>    EOF
>    qemu-system-i386: exec.c:3621: address_space_unmap: Assertion `mr != NULL' failed.
>    Aborted (core dumped)
> 
> This is because we don't check the return value from dma_memory_map()
> which can return NULL, then we call dma_memory_unmap(NULL) which is
> illegal. Fix by only unmap if the value is not NULL (and the size is
> not the expected one).
> 
> Cc: qemu-stable@nongnu.org
> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> Fixes: f6ad2e32f8 ("ahci: add ahci emulation")
> BugLink: https://bugs.launchpad.net/qemu/+bug/1884693
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>   hw/ide/ahci.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
> index 009120f88b..4f596cb9ce 100644
> --- a/hw/ide/ahci.c
> +++ b/hw/ide/ahci.c
> @@ -250,7 +250,7 @@ static void map_page(AddressSpace *as, uint8_t **ptr, uint64_t addr,
>       }
>   
>       *ptr = dma_memory_map(as, addr, &len, DMA_DIRECTION_FROM_DEVICE);
> -    if (len < wanted) {
> +    if (len < wanted && *ptr) {
>           dma_memory_unmap(as, *ptr, len, DMA_DIRECTION_FROM_DEVICE, len);
>           *ptr = NULL;
>       }
> 

Staged @ gitlab

https://gitlab.com/jsnow/qemu/-/commits/ide

Patchew 2.1-devel-b67e4c2

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