powerpc: Do not restore KUAP in arch_exit_to_user_mode_prepare()
In the Linux kernel, the following vulnerability has been resolved: powerpc: Do not restore KUAP in arch_exit_to_user_mode_prepare() KUAP means kernel cannot touch user memory unless it explicitly is enabled. In the kernel it should stay AMR_KUAP_BLOCKED. While returning to userspace just before RFI, kernel should restore the user AMR value back. Looks like GENERIC_ENTRY might be treating arch_exit_to_user_mode_prepare() as the last architecture step before returning to userspace. commit bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY feature") therefore called kuap_user_restore() from that hook. But on PowerPC that is too early. After irqentry_exit() / syscall_exit_to_user_mode() we still run platform specific exit routines. e.g. code snippets showing both exception handling and system call handling as the callers of function arch_exit_to_user_mode_prepare() which does kuap_user_restore(). The below path shows that calling kuap_user_restore() is too early when called from arch_exit_to_user_mode_prepare(). Exception handling in exceptions-64s.S ======================================= bl CFUNC(do_page_fault) ..DEFINE_INTERRUPT_HANDLER_ASYNC(do_page_fault) arch_interrupt_async_enter_prepare(regs); state = irqentry_enter(regs); instrumentation_begin(); irq_enter_rcu(); handler(regs); nap_adjust_return(regs); irq_exit_rcu(); instrumentation_end(); arch_interrupt_async_exit_prepare(regs); irqentry_exit(regs, state); <<< too early irqentry_exit_to_user_mode() __exit_to_user_mode_prepa
CVE-2026-98396
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-98396
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "02565a782c1ee7e8ada38ad24a698e01d6ea9ff8",
"lessThan": "c8e80c19c3b9c8db83a14fab00445a6064992442",
"versionType": "git"
},
{
"status": "affected",
"version": "02565a782c1ee7e8ada38ad24a698e01d6ea9ff8",
"lessThan": "c2549d749539487239475fbc8c614a1f9244d655",
"versionType": "git"
}
],
"programFiles": [
"arch/powerpc/include/asm/entry-common.h"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "7.2"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "7.2",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "7.2.7",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"arch/powerpc/include/asm/entry-common.h"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-98396
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #38463 · Revision 1
- Added to Heist Feed
- Publisher date