Re: [PATCH 02/15] elf: Fix data race in _dl_name_match_p [BZ #21349]

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

The 04/01/2021 11:01, Adhemerval Zanella wrote:
> On 15/02/2021 08:56, Szabolcs Nagy via Libc-alpha wrote:
> > From: Maninder Singh <maninder1.s@samsung.com>
> > 
> > dlopen updates libname_list by writing to lastp->next, but concurrent
> > reads in _dl_name_match_p were not synchronized when it was called
> > without holding GL(dl_load_lock), which can happen during lazy symbol
> > resolution.
> > 
> > This patch fixes the race between _dl_name_match_p reading lastp->next
> > and add_name_to_object writing to it. This could cause segfault on
> > targets with weak memory order when lastp->next->name is read, which
> > was observed on an arm system. Fixes bug 21349.
> > 
> > (Code is from Maninder Singh, comments and description is from Szabolcs
> > Nagy.)
> > 
> > Co-authored-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
> 
> I couldn't reproduce with the example provided in the bugzilla (on both
> aarch64 and arm machines), but the explanation and the fix sounds logical.
> I guess a testcase will be hard to create an exercise the issue.
> 
> LGTM, thanks.
> 
> Reviewed-by; Adhemerval Zanella  <adhemerval.zanella@linaro.org>

thanks, committed at 395be7c2184645320c955b0ba214af9fa1ea9675