On Wed, 2026-08-12 at 02:28 -0500, Junjie Cao wrote: > KPTI clones the kernel entry text into the user page tables at its > KASLR-slid address and, on CPUs with PGE, sets the global bit on those > PTEs. The mapping survives the CR3 write on kernel exit, and a local > attacker can time prefetch instructions across the kernel range to > recover the KASLR base in well under a second. > > Disclosure and write-up: > > https://www.openwall.com/lists/oss-security/2022/12/16/3 > https://www.willsroot.io/2022/12/entrybleed.html > > The disclosure states that after discussion with [email protected] and > linux-distros "a fix for this is currently not available", and none has > appeared since; arch/x86/mm/pti.c still clones the entry text and sets > _PAGE_GLOBAL on the cloned PTEs. This is an unfixed issue, not a stated > wontfix - Debian notes "Ignored upstream and KASLR is not expected to be > resistant to local attacks", Ubuntu has it deferred since 2023-01-10: > > https://security-tracker.debian.org/tracker/CVE-2022-4543 > https://ubuntu.com/security/CVE-2022-4543 > > 97e3d26b5e5f ("x86/mm: Randomize per-cpu entry area", v6.2) randomizes > the separate cpu_entry_area; it predates this disclosure and does not > change the offset of entry_SYSCALL_64 from the KASLR base.
There's too much unnecessary detail here. Drop the mention of a commit that doesn't fix the issue, you don't need to say "not a stated wontfix", etc. > > CC: Paul Barker <[email protected]> > AI-Generated: Uses Claude (claude-opus-5) > Signed-off-by: Junjie Cao <[email protected]> > --- > v3: > - use "unpatched" instead of "upstream-wontfix": the security-team > discussion produced no clear wontfix decision > > v2: > https://lore.kernel.org/openembedded-core/[email protected]/ > > meta/recipes-kernel/linux/cve-exclusion.inc | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/meta/recipes-kernel/linux/cve-exclusion.inc > b/meta/recipes-kernel/linux/cve-exclusion.inc > index b08eaa1..a909aef 100644 > --- a/meta/recipes-kernel/linux/cve-exclusion.inc > +++ b/meta/recipes-kernel/linux/cve-exclusion.inc > @@ -229,3 +229,11 @@ was never substantiated and was closed as not-a-bug by > Red Hat, SUSE and Debian" > # Fix https://git.kernel.org/linus/d860d1faa6b2ce3becfdb8b0c2b048ad31800061 > # Fix https://git.kernel.org/linus/da9c9c877597170b929a6121a68dcd3dd9a80f45 > CVE_STATUS[CVE-2022-1247] = "fixed-version: Fixed from version 6.17" > + > +# "EntryBleed": KPTI maps the entry text into the user page tables with > +# the global bit set, leaking the KASLR base by prefetch timing. Discussed > +# with the kernel security team; no fix, KASLR is not treated as a boundary > +# against local attackers. Distinct from CVE-2023-3640 (cpu_entry_area). > +# https://www.willsroot.io/2022/12/entrybleed.html > +CVE_STATUS[CVE-2022-4543] = "unpatched: no upstream fix, KASLR is not \ > +treated as a defence against local attackers" Suggested wording, links and include triage date: # Triaged August 2026 - "EntryBleed", discussed with the kernel security team # but no fix appears to have been published since then. Debian says "Ignored # upstream and KASLR is not expected to be resistant to local attacks", fix # deferred in Ubuntu. # https://www.openwall.com/lists/oss-security/2022/12/16/3 # https://security-tracker.debian.org/tracker/CVE-2022-4543 # https://ubuntu.com/security/CVE-2022-4543 CVE_STATUS[CVE-2022-4543] = "unpatched: No fix has been proposed" Best regards, -- Paul Barker
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