x86/pkeys: Fix pkey_alloc() return value when pkeys are not supported

Browse source

The man page for pkey_alloc(2) specifies that it should return -1 with
the errno set to ENOSPC when pkeys are not supported [1]. However, on
x86 pkey_alloc() sets errno to EINVAL when called for the first time
on a CPU that does not support pkeys.

The root cause of this is the x86 implementation of mm_pkey_alloc() not
directly checking if pkeys are supported. It only checks if all the
pkeys have been allocated by comparing the allocation map against
all_pkeys_mask. When OSPKE is not enabled, init_new_context() skips the
initialization of the allocation map, leaving it as 0, while
all_pkeys_mask is 1. mm_pkey_alloc() interprets this as there being a
pkey available and it returns pkey 0. Then, pkey_alloc() fails with
-EINVAL from arch_set_user_pkey_access() instead of returning -ENOSPC.
Subsequent calls to pkey_alloc() do return -ENOSPC because pkey 0 is
left marked as allocated.

Change mm_pkey_alloc() to directly check if OSPKE is enabled, and
return -1 if it is not, which causes pkey_alloc() to return -ENOSPC. The
arm64 and powerpc implementations of mm_pkey_alloc() already do this
check.

[1] https://man7.org/linux/man-pages/man2/pkey_alloc.2.html

[ dhansen: use arch_pkeys_enabled() to follow arm ]

Fixes: e8c24d3a23 ("x86/pkeys: Allocation/free syscalls")
Signed-off-by: Bijan Tabatabai <btabatabai@wisc.edu>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20260716220604.26452-1-bijan311@gmail.com

...

This commit is contained in:

Bijan Tabatabai 2026-07-16 17:06:04 -05:00 • committed by Dave Hansen

parent 7da514d819

commit dee87e09b0

1 changed files with 3 additions and 0 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

3

arch/x86/include/asm/pkeys.h

View file