Patchwork fix ELF loading for 0-length sections

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Submitter Damian, Alexandru
Date Feb. 21, 2012, 10:42 a.m.
Message ID <CAJ2CSBteCm19_DKfastsxAR0chQGRzAZOjPjs0Nw-ySsyCk1YA@mail.gmail.com>
Download mbox | patch
Permalink /patch/142279/
State New
Headers show

Comments

Damian, Alexandru - Feb. 21, 2012, 10:42 a.m.
Hi,

I got a problem with QEMU refusing to load an ELF binary with 0-length
sections,
while the kernel has no issue doing this.

This patch adds a check that has been in kernel since 2008 at least.

Cheers,
Alex

----------------
commit a42e5231c1be5f09caeb6c73e34933cd7efa7023
Author: Alexandru DAMIAN <alexandru.damian@intel.com>
Date:   Tue Feb 21 12:34:36 2012 +0200

    Do not attempt to map 0-length sections

    Mmap will return an invalid argument, but 0-length sections
    are valid in any case. The kernel as a similar check
    when loading elf binaries courtesy of jkosina@suse.cz.

    Signed-off-by: Alexandru Damian <alexandru.damian@intel.com>

image_info *infop)
 {
@@ -1565,11 +1565,16 @@ static void load_elf_image(const char *image_name,
int image_fd,
             vaddr_po = TARGET_ELF_PAGEOFFSET(vaddr);
             vaddr_ps = TARGET_ELF_PAGESTART(vaddr);

-            error = target_mmap(vaddr_ps, eppnt->p_filesz + vaddr_po,
-                                elf_prot, MAP_PRIVATE | MAP_FIXED,
-                                image_fd, eppnt->p_offset - vaddr_po);
-            if (error == -1) {
-                goto exit_perror;
+            /* Don't attempt to map 0 bytes len sections.
+               Kernel also has this check.
+            */
+            if (eppnt->p_filesz + vaddr_po != 0) {
+                    error = target_mmap(vaddr_ps, eppnt->p_filesz +
vaddr_po,
+                                        elf_prot, MAP_PRIVATE | MAP_FIXED,
+                                        image_fd, eppnt->p_offset -
vaddr_po);
+                    if (error == -1) {
+                        goto exit_perror;
+                    }
             }

             vaddr_ef = vaddr + eppnt->p_filesz;
Peter Maydell - Feb. 21, 2012, 11:08 a.m.
On 21 February 2012 10:42, Damian, Alexandru <alexandru.damian@intel.com> wrote:
> Hi,
>
> I got a problem with QEMU refusing to load an ELF binary with 0-length
> sections,
> while the kernel has no issue doing this.
>
> This patch adds a check that has been in kernel since 2008 at least.

CC'ing Riku (linux-user maintainer).

>
> Cheers,
> Alex
>
> ----------------
> commit a42e5231c1be5f09caeb6c73e34933cd7efa7023
> Author: Alexandru DAMIAN <alexandru.damian@intel.com>
> Date:   Tue Feb 21 12:34:36 2012 +0200
>
>     Do not attempt to map 0-length sections
>
>     Mmap will return an invalid argument, but 0-length sections
>     are valid in any case. The kernel as a similar check
>     when loading elf binaries courtesy of jkosina@suse.cz.
>
>     Signed-off-by: Alexandru Damian <alexandru.damian@intel.com>

Convention is to submit patches as git-format-patch style emails.

> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index ea61d0d..71d0ae3 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -918,9 +918,9 @@ static inline void init_thread(struct target_pt_regs
> *regs,
>
>  #define elf_check_arch(x) ( (x) == ELF_ARCH )
>
> -#define ELF_CLASS    ELFCLASS64
> -#define ELF_DATA    ELFDATA2MSB
> -#define ELF_ARCH    EM_S390
> +#define ELF_CLASS        ELFCLASS64
> +#define ELF_DATA        ELFDATA2MSB
> +#define ELF_ARCH        EM_S390

Please don't make unrelated whitespace changes.

>
>  static inline void init_thread(struct target_pt_regs *regs, struct
> image_info *infop)
>  {
> @@ -1565,11 +1565,16 @@ static void load_elf_image(const char *image_name,
> int image_fd,
>              vaddr_po = TARGET_ELF_PAGEOFFSET(vaddr);
>              vaddr_ps = TARGET_ELF_PAGESTART(vaddr);
>
> -            error = target_mmap(vaddr_ps, eppnt->p_filesz + vaddr_po,
> -                                elf_prot, MAP_PRIVATE | MAP_FIXED,
> -                                image_fd, eppnt->p_offset - vaddr_po);
> -            if (error == -1) {
> -                goto exit_perror;
> +            /* Don't attempt to map 0 bytes len sections.
> +               Kernel also has this check.
> +            */

This comment could be better:
   /* mmap() will fail EINVAL if given a zero size, but a
    * segment with zero filesize is perfectly valid (and
    * handled by the kernel's ELF loading code).
    */

> +            if (eppnt->p_filesz + vaddr_po != 0) {
> +                    error = target_mmap(vaddr_ps, eppnt->p_filesz +
> vaddr_po,
> +                                        elf_prot, MAP_PRIVATE | MAP_FIXED,
> +                                        image_fd, eppnt->p_offset -
> vaddr_po);

Something in your patch submission path is wrapping long lines.

> +                    if (error == -1) {
> +                        goto exit_perror;
> +                    }

QEMU coding style is four-space indents, but the indent in your new
code is mostly eight-space.

>              }
>
>              vaddr_ef = vaddr + eppnt->p_filesz;
>

Otherwise looks OK.

-- PMM
Damian, Alexandru - Feb. 25, 2012, 8:48 a.m.
Hi guys,

Please don't submit these patches yet - I will re-submit from a different
email, to lessen the
legal complications.

I'm also adding a couple of new patches - just a heads up, when
transferring structs or arrays
in a syscall/ioctl, pointers also need conversions between target memory
space and host memory space.

i.e.
#if HOST_LONG_BITS == 32 && TARGET_ABI_BITS == 32
    case TYPE_LONG:
    case TYPE_ULONG:
        *(uint32_t *)dst = tswap32(*(uint32_t *)src);
        break;
    case TYPE_PTRVOID:
    /* we actually convert pointer values between host and target */
        if (to_host) {
                *(uint32_t *)dst = (uint32_t)g2h(*(uint32_t*)src);
        }
        else {
                *(uint32_t *)dst = (uint32_t)h2g(*(uint32_t*)src);
        }
        break;

Cheers,
Alex

On Tue, Feb 21, 2012 at 3:08 AM, Peter Maydell <peter.maydell@linaro.org>wrote:

> On 21 February 2012 10:42, Damian, Alexandru <alexandru.damian@intel.com>
> wrote:
> > Hi,
> >
> > I got a problem with QEMU refusing to load an ELF binary with 0-length
> > sections,
> > while the kernel has no issue doing this.
> >
> > This patch adds a check that has been in kernel since 2008 at least.
>
> CC'ing Riku (linux-user maintainer).
>
> >
> > Cheers,
> > Alex
> >
> > ----------------
> > commit a42e5231c1be5f09caeb6c73e34933cd7efa7023
> > Author: Alexandru DAMIAN <alexandru.damian@intel.com>
> > Date:   Tue Feb 21 12:34:36 2012 +0200
> >
> >     Do not attempt to map 0-length sections
> >
> >     Mmap will return an invalid argument, but 0-length sections
> >     are valid in any case. The kernel as a similar check
> >     when loading elf binaries courtesy of jkosina@suse.cz.
> >
> >     Signed-off-by: Alexandru Damian <alexandru.damian@intel.com>
>
> Convention is to submit patches as git-format-patch style emails.
>
> > diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> > index ea61d0d..71d0ae3 100644
> > --- a/linux-user/elfload.c
> > +++ b/linux-user/elfload.c
> > @@ -918,9 +918,9 @@ static inline void init_thread(struct target_pt_regs
> > *regs,
> >
> >  #define elf_check_arch(x) ( (x) == ELF_ARCH )
> >
> > -#define ELF_CLASS    ELFCLASS64
> > -#define ELF_DATA    ELFDATA2MSB
> > -#define ELF_ARCH    EM_S390
> > +#define ELF_CLASS        ELFCLASS64
> > +#define ELF_DATA        ELFDATA2MSB
> > +#define ELF_ARCH        EM_S390
>
> Please don't make unrelated whitespace changes.
>
> >
> >  static inline void init_thread(struct target_pt_regs *regs, struct
> > image_info *infop)
> >  {
> > @@ -1565,11 +1565,16 @@ static void load_elf_image(const char
> *image_name,
> > int image_fd,
> >              vaddr_po = TARGET_ELF_PAGEOFFSET(vaddr);
> >              vaddr_ps = TARGET_ELF_PAGESTART(vaddr);
> >
> > -            error = target_mmap(vaddr_ps, eppnt->p_filesz + vaddr_po,
> > -                                elf_prot, MAP_PRIVATE | MAP_FIXED,
> > -                                image_fd, eppnt->p_offset - vaddr_po);
> > -            if (error == -1) {
> > -                goto exit_perror;
> > +            /* Don't attempt to map 0 bytes len sections.
> > +               Kernel also has this check.
> > +            */
>
> This comment could be better:
>   /* mmap() will fail EINVAL if given a zero size, but a
>    * segment with zero filesize is perfectly valid (and
>    * handled by the kernel's ELF loading code).
>     */
>
> > +            if (eppnt->p_filesz + vaddr_po != 0) {
> > +                    error = target_mmap(vaddr_ps, eppnt->p_filesz +
> > vaddr_po,
> > +                                        elf_prot, MAP_PRIVATE |
> MAP_FIXED,
> > +                                        image_fd, eppnt->p_offset -
> > vaddr_po);
>
> Something in your patch submission path is wrapping long lines.
>
> > +                    if (error == -1) {
> > +                        goto exit_perror;
> > +                    }
>
> QEMU coding style is four-space indents, but the indent in your new
> code is mostly eight-space.
>
> >              }
> >
> >              vaddr_ef = vaddr + eppnt->p_filesz;
> >
>
> Otherwise looks OK.
>
> -- PMM
>

Patch

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index ea61d0d..71d0ae3 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -918,9 +918,9 @@  static inline void init_thread(struct target_pt_regs
*regs,

 #define elf_check_arch(x) ( (x) == ELF_ARCH )

-#define ELF_CLASS    ELFCLASS64
-#define ELF_DATA    ELFDATA2MSB
-#define ELF_ARCH    EM_S390
+#define ELF_CLASS        ELFCLASS64
+#define ELF_DATA        ELFDATA2MSB
+#define ELF_ARCH        EM_S390

 static inline void init_thread(struct target_pt_regs *regs, struct