On Mon, Jan 23, 2017 at 11:46 AM, Justin Cinkelj <justin.cink...@xlab.si>
wrote:
> Code to remove \0 at end of string tried to copy strlen()-1 data bytes.
> It didn't expect the .note.osv-mlock section to contains only 0x00.
> This caused attempt to allocate and copy -1 bytes, converted to about 4GB.
>
> Commit addes extra check for the 0-length string case.
>
> Fixes 840.
>
> Signed-off-by: Justin Cinkelj <justin.cink...@xlab.si>
> ---
> core/elf.cc | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/core/elf.cc b/core/elf.cc
> index efa574e..ab4535d 100644
> --- a/core/elf.cc
> +++ b/core/elf.cc
> @@ -26,6 +26,7 @@
> #include <osv/stubbing.hh>
> #include <sys/utsname.h>
> #include <osv/demangle.hh>
> +#include <algorithm>
>
> #include "arch.hh"
>
> @@ -360,9 +361,12 @@ Elf64_Note::Elf64_Note(void *_base, char *str)
> // The note section strings will include the trailing 0. std::string
> // doesn't like that very much, and comparisons against a string that
> is
> // constructed from this string will fail. Therefore the - 1 at the
> end
> - n_owner.assign(str, base[0] - 1);
> + Elf64_Word len;
> + len = std::max(base[0], (Elf64_Word)1) - 1;
> + n_owner.assign(str, len);
>
Thanks. This is correct, but I just wonder if it wouldn't be clearer to
simply not call assign() at all for an empty string - instead of these
three lines, do
if (base[0]) {
n_owner.assign(str, base[0] - 1);
}
If we don't call assign(), the string will remain with its default value,
i.e., empty.
str = align_up(str + base[0], 4);
> - n_value.assign(str, base[1] - 1);
> + len = std::max(base[1], (Elf64_Word)1) - 1;
> + n_value.assign(str, len);
> }
>
> void object::load_segments()
> --
> 2.9.3
>
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