[Bug dynamic-link/27181] New: __tunables_init can oom fail

[Bug dynamic-link/27181] New: __tunables_init can oom fail

[nsz at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27181

            Bug ID: 27181
           Summary: __tunables_init can oom fail
           Product: glibc
           Version: 2.32
            Status: NEW
          Severity: normal
          Priority: P2
         Component: dynamic-link
          Assignee: unassigned at sourceware dot org
          Reporter: nsz at gcc dot gnu.org
  Target Milestone: ---

__tunables_init happens very early (before libc ifunc
resolvers are run).

it should not unnecessarily introduce failures, but
it allocates memory in tunables_strdup. this is only
needed in setuid executables when the GLIBC_TUNABLES
env var has to be sanitized, so there should be no
failure mode in other cases.

with static pie __tunables_init will happen before self
relocation (after bug 27072 is fixed) so complex code
like _dl_fatal_printf should not be used there otherwise
it's hard to guarantee that there are no relocations.

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[Bug dynamic-link/27181] __tunables_init can oom fail

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27181

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Szabolcs Nagy <nsz@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=bfe04789a8d9014cf3177137651f8f93dd4a00ca

commit bfe04789a8d9014cf3177137651f8f93dd4a00ca
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Tue Jan 12 16:28:27 2021 +0000

    elf: Avoid RELATIVE relocs in __tunables_init

    With static pie linking pointers in the tunables list need
    RELATIVE relocs since the absolute address is not known at link
    time. We want to avoid relocations so the static pie self
    relocation can be done after tunables are initialized.

    This is a simple fix that embeds the tunable strings into the
    tunable list instead of using pointers.  It is possible to have
    a more compact representation of tunables with some additional
    complexity in the generator and tunable parser logic.  Such
    optimization will be useful if the list of tunables grows.

    There is still an issue that tunables_strdup allocates and the
    failure handling code path is sufficiently complex that it can
    easily have RELATIVE relocations.  It is possible to avoid the
    early allocation and only change environment variables in a
    setuid exe after relocations are processed.  But that is a
    bigger change and early failure is fatal anyway so it is not
    as critical to fix right away. This is bug 27181.

    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

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[Bug dynamic-link/27181] __tunables_init can oom fail

[adhemerval.zanella at linaro dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27181

Adhemerval Zanella <adhemerval.zanella at linaro dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
                 CC|                            |adhemerval.zanella at linaro dot o
                   |                            |rg
   Target Milestone|---                         |2.39

--- Comment #2 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
Fixed on 2.39 (commit 2a969b53c0b02fed7e43473a92f219d737fd217a).

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