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prctl: Disable prctl(PR_SET_MDWE) on parisc

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systemd-254 tries to use prctl(PR_SET_MDWE) for it's MemoryDenyWriteExecute
functionality, but fails on parisc which still needs executable stacks in
certain combinations of gcc/glibc/kernel.

Disable prctl(PR_SET_MDWE) by returning -EINVAL for now on parisc, until
userspace has catched up.

Signed-off-by: Helge Deller <deller@gmx.de>
Co-developed-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Sam James <sam@gentoo.org>
Closes: https://github.com/systemd/systemd/issues/29775
Tested-by: Sam James <sam@gentoo.org>
Link: https://lore.kernel.org/all/875y2jro9a.fsf@gentoo.org/
Cc: <stable@vger.kernel.org> # v6.3+
This commit is contained in:
Helge Deller 2023-11-18 19:33:35 +01:00
parent 6ad6e15a9c
commit 793838138c
1 changed files with 4 additions and 0 deletions
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4
kernel/sys.c
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@ -2394,6 +2394,10 @@ static inline int prctl_set_mdwe(unsigned long bits, unsigned long arg3,
if (bits & PR_MDWE_NO_INHERIT && !(bits & PR_MDWE_REFUSE_EXEC_GAIN))
return -EINVAL;
/* PARISC cannot allow mdwe as it needs writable stacks */
if (IS_ENABLED(CONFIG_PARISC))
return -EINVAL;
current_bits = get_current_mdwe();
if (current_bits && current_bits != bits)
return -EPERM; /* Cannot unset the flags */