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linux/tools/testing/selftests/exec
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Kees Cook 3545deff0e binfmt_elf: Honor PT_LOAD alignment for static PIE 
The p_align values in PT_LOAD were ignored for static PIE executables
(i.e. ET_DYN without PT_INTERP). This is because there is no way to
request a non-fixed mmap region with a specific alignment. ET_DYN with
PT_INTERP uses a separate base address (ELF_ET_DYN_BASE) and binfmt_elf
performs the ASLR itself, which means it can also apply alignment. For
the mmap region, the address selection happens deep within the vm_mmap()
implementation (when the requested address is 0).

The earlier attempt to implement this:

  commit 9630f0d60f ("fs/binfmt_elf: use PT_LOAD p_align values for static PIE")
  commit 925346c129 ("fs/binfmt_elf: fix PT_LOAD p_align values for loaders")

did not take into account the different base address origins, and were
eventually reverted:

  aeb7923733 ("revert "fs/binfmt_elf: use PT_LOAD p_align values for static PIE"")

In order to get the correct alignment from an mmap base, binfmt_elf must
perform a 0-address load first, then tear down the mapping and perform
alignment on the resulting address. Since this is slightly more overhead,
only do this when it is needed (i.e. the alignment is not the default
ELF alignment). This does, however, have the benefit of being able to
use MAP_FIXED_NOREPLACE, to avoid potential collisions.

With this fixed, enable the static PIE self tests again.

Reported-by: H.J. Lu <hjl.tools@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=215275
Link: https://lore.kernel.org/r/20240508173149.677910-3-keescook@chromium.org
Signed-off-by: Kees Cook <kees@kernel.org>
History 2024-06-19 12:45:06 -07:00
..
.gitignore selftests/exec: add generated files to .gitignore 2022-03-03 15:17:04 -07:00
binfmt_script.py selftests/exec: binfmt_script: Add the overall result line according to TAP 2024-03-13 11:53:45 -07:00
execveat.c selftests/exec: execveat: Improve debug reporting 2024-03-18 11:19:37 -07:00
load_address.c selftests/exec: Build both static and non-static load_address tests 2024-06-19 12:44:39 -07:00
Makefile binfmt_elf: Honor PT_LOAD alignment for static PIE 2024-06-19 12:45:06 -07:00
non-regular.c selftests/exec: add file type errno tests 2020-08-14 19:56:56 -07:00
null-argv.c selftests/exec: Test for empty string on NULL argv 2022-03-01 16:16:27 -08:00
recursion-depth.c selftests: exec: Use new ksft_exit_fail_perror() helper 2024-05-06 13:57:19 -06:00