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Differential D27953

rtld: When relocating, map without PROT_EXEC
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Authored by emaste on Jan 4 2021, 5:44 PM.
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bdragon

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kib
val_packett.cool
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rG065f8cea1b8e: rtld: map without PROT_EXEC for relocation
rG613a08cfa2e0: rtld: map without PROT_EXEC for relocation
Summary

This makes text segment relocation work under W^X.

I have encountered this when loading lucet-compiled shared objects with W^X (D24933).

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Event Timeline

val_packett.cool created this revision.Jan 4 2021, 5:44 PM
Herald added a subscriber: bdragon. · View Herald TranscriptJan 4 2021, 5:44 PM
val_packett.cool requested review of this revision.Jan 4 2021, 5:44 PM
val_packett.cool added a parent revision: D24933: implement W^X for mmap and mprotect.
emaste added a reviewer: kib.Jan 4 2021, 5:51 PM
emaste added inline comments.Jan 4 2021, 6:00 PM
libexec/rtld-elf/rtld.c
2986–2987

maybe clearer if we incorporate the PROT_WRITE part from above?

something like

prot = convert_prot(ph->p_flags);
if (before)
        prot = prot & ~PROT_EXEC | PROT_WRITE;
kib added inline comments.Jan 4 2021, 6:42 PM
libexec/rtld-elf/rtld.c
2986–2987

There is no much reason to use convert_prot() in'before' case at all, then. Only PF_R survives. It can be

prot = before ? (PROT_READ | PROT_WRITE) : convert_prot(ph->p_flags);
emaste added a comment.Jan 4 2021, 7:03 PM

Added to my staging tree here: https://github.com/emaste/freebsd/commit/138b3637e80a4ececdc0eaf8aea734262217d0b0

emaste commandeered this revision.Jan 5 2021, 2:16 PM
emaste updated this revision to Diff 81672.
emaste edited reviewers, added: val_packett.cool; removed: emaste.

Update per kib's suggestion

kib accepted this revision.Jan 5 2021, 3:04 PM
This revision is now accepted and ready to land.Jan 5 2021, 3:04 PM
Closed by commit rG613a08cfa2e0: rtld: map without PROT_EXEC for relocation (authored by emaste). · Explain WhyJan 5 2021, 3:58 PM
This revision was automatically updated to reflect the committed changes.
emaste added a commit: rG613a08cfa2e0: rtld: map without PROT_EXEC for relocation.
emaste added a commit: rG065f8cea1b8e: rtld: map without PROT_EXEC for relocation.Jan 19 2021, 2:47 AM

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libexec/
rtld-elf/
3 lines

Diff 81672

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libexec/rtld-elf/rtld.c

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