[Bug libelf/21315] New: multiple misaligned address errors

[Bug libelf/21315] New: multiple misaligned address errors

[ago at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=21315

            Bug ID: 21315
           Summary: multiple misaligned address errors
           Product: elfutils
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libelf
          Assignee: unassigned at sourceware dot org
          Reporter: ago at gentoo dot org
                CC: elfutils-devel at sourceware dot org
  Target Milestone: ---

Created attachment 9947
  --> https://sourceware.org/bugzilla/attachment.cgi?id=9947&action=edit
errors

On elfutils-0.168:

# eu-elflint -d $FILE
libelf/elf32_getshdr.c:140:8: runtime error: member access within misaligned
address 0x7fa161766002 for type 'struct Elf64_Shdr', which requires 8 byte
alignment


Compiled with: gcc-6.3.0
Visible with: -fsanitize=undefined

Reproducer:
https://github.com/asarubbo/poc/blob/master/00237-elfutils-misalignedaddress1

Errors attached.

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[Bug libelf/21315] multiple misaligned address errors for Elf64_Shdr

[ago at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=21315

Agostino Sarubbo <ago at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|multiple misaligned address |multiple misaligned address
                   |errors                      |errors for Elf64_Shdr

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[Bug libelf/21315] multiple misaligned address errors for Elf64_Shdr

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=21315

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mark at klomp dot org

--- Comment #1 from Mark Wielaard <mark at klomp dot org> ---
Note that in some cases elfutils deliberately does unaligned accesses if it
believes it is safe. See the following in lib/eu-config.h:

/* Define ALLOW_UNALIGNED if the architecture allows operations on
   unaligned memory locations.  */
#define SANITIZE_UNDEFINED 1
#if (defined __i386__ || defined __x86_64__) && ! CHECK_UNDEFINED
# define ALLOW_UNALIGNED        1
#else
# define ALLOW_UNALIGNED        0
#endif

Note that it is to not allow unaligned accesses when configuring with
--enable-sanitize-undefined (which adds -fsanitize=undefined
-fno-sanitize-recover to CFLAGS and CXXFLAGS).

Are you configuring using --enable-sanitize-undefined? Or adding
-fsanitize=undefined by hand? In the later case you should also add
-DCHECK_UNDEFINED=1

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[Bug libelf/21315] multiple misaligned address errors for Elf64_Shdr

[ago at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=21315

--- Comment #2 from Agostino Sarubbo <ago at gentoo dot org> ---
(In reply to Mark Wielaard from comment #1)
> Note that in some cases elfutils deliberately does unaligned accesses if it
> believes it is safe. See the following in lib/eu-config.h:
> 
> /* Define ALLOW_UNALIGNED if the architecture allows operations on
>    unaligned memory locations.  */
> #define SANITIZE_UNDEFINED 1
> #if (defined __i386__ || defined __x86_64__) && ! CHECK_UNDEFINED
> # define ALLOW_UNALIGNED        1
> #else
> # define ALLOW_UNALIGNED        0
> #endif
> 
> Note that it is to not allow unaligned accesses when configuring with
> --enable-sanitize-undefined (which adds -fsanitize=undefined
> -fno-sanitize-recover to CFLAGS and CXXFLAGS).
> 
> Are you configuring using --enable-sanitize-undefined? Or adding
> -fsanitize=undefined by hand? In the later case you should also add
> -DCHECK_UNDEFINED=1

It was added by hand..I need to test if I obtain those warning with
--enable-sanitize-undefined

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[Bug libelf/21315] multiple misaligned address errors for Elf64_Shdr

[ago at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=21315

--- Comment #3 from Agostino Sarubbo <ago at gentoo dot org> ---
Mark,

I do not have enough resources to make again my tests. Let's close this an the
other similar report for now, I'll reopen them in the future in case will be
needed.

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[Bug libelf/21315] multiple misaligned address errors for Elf64_Shdr

[mark at klomp dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=21315

Mark Wielaard <mark at klomp dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |OBSOLETE

--- Comment #4 from Mark Wielaard <mark at klomp dot org> ---
Thanks. Closing for now.

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