Re: [Xen-devel] [PATCH v4 1/9] livepatch: Clear .bss when payload is reverted

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.09.16 at 18:47, <konrad.wilk@xxxxxxxxxx> wrote:
> On Wed, Aug 24, 2016 at 02:55:21AM -0600, Jan Beulich wrote:
>> >>> On 24.08.16 at 04:22, <konrad.wilk@xxxxxxxxxx> wrote:
>> > --- a/xen/common/livepatch.c
>> > +++ b/xen/common/livepatch.c
>> > @@ -70,6 +70,9 @@ struct payload {
>> >      unsigned int nsyms;                  /* Nr of entries in .strtab and 
>> > symbols. */
>> >      struct livepatch_build_id id;        /* 
>> > ELFNOTE_DESC(.note.gnu.build-id) of the payload. */
>> >      struct livepatch_build_id dep;       /* 
>> > ELFNOTE_DESC(.livepatch.depends). */
>> > +    void **bss;                          /* .bss's of the payload. */
>> > +    size_t *bss_size;                    /* and their sizes. */
>> 
>> Is size_t wide enough in the extreme case? Perhaps yes, because I
>> don't think we'll ever load 64-bit ELF on a 32-bit platform.
> 
> Nonethless having a huge .bss is a kind of extreme? Perhaps we should
> have an seperate patch that checks the SHT_NOBITS and disallows .bss's
> bigger than say 2MB?

Well, the extra check certainly wouldn't hurt, but I think before
hitting the size_t limit you'd run out of address space to place
the payload in (as that's iirc a less than 1Gb area).

Jan


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