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Bump version to 4.18.0-553.124.4

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ptrace: require CAP_SYS_PTRACE when task has no mm

kABI-safe AlmaLinux backport of upstream commit 31e62c2ebbfd
("ptrace: slightly saner 'get_dumpable()' logic"). The upstream
fix adds a user_dumpable bit to task_struct and caches it from
exit_mm() -- both layout changes would break the kABI signature
of struct task_struct (referenced by stablelist exports such as
__put_task_struct, sched_setscheduler, set_cpus_allowed_ptr, and
wake_up_process).

Instead, take the minimal kABI-safe slice: in __ptrace_may_access(),
when task->mm == NULL, require CAP_SYS_PTRACE in init_user_ns
unconditionally. This closes the Qualys Security Advisory hole
without touching task_struct or exit.c. The only behavioural
delta versus upstream is that an already-exited user task whose
mm has been cleared now also requires CAP_SYS_PTRACE.
This commit is contained in:
Andrew Lukoshko 2026-05-15 07:33:28 +00:00 committed by Andrew Lukoshko
parent e1dbabe6cc
commit 053da2e7bb
2 changed files with 62 additions and 2 deletions
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55
SOURCES/1101-ptrace-require-cap-on-mm-less-task.patch Normal file
View File

@ -0,0 +1,55 @@
From: Andrew Lukoshko <alukoshko@almalinux.org>
Subject: [PATCH AlmaLinux 8] ptrace: require CAP_SYS_PTRACE when task has no mm
kABI-safe AlmaLinux backport of upstream commit 31e62c2ebbfd
("ptrace: slightly saner 'get_dumpable()' logic") posted at
https://github.com/torvalds/linux/commit/31e62c2ebbfdc3fe3dbdf5e02c92a9dc67087a3a
The upstream fix adds a 'user_dumpable:1' bit to task_struct and
caches the last dumpability in exit_mm() so __ptrace_may_access()
can require CAP_SYS_PTRACE when the target has no mm (e.g. kernel
threads or already-exited user tasks). That layout change to
task_struct breaks kABI on RHEL/AlmaLinux 8 (the symtype
signature of struct task_struct is referenced by stablelist exports
such as set_cpus_allowed_ptr() and wake_up_process()), so we cannot
import the field/exit_mm hunks as-is.
Take the minimal kABI-safe slice instead: when task->mm == NULL,
require CAP_SYS_PTRACE in init_user_ns unconditionally. This closes
the Qualys Security Advisory hole -- mm-less targets no longer pass
the dumpability check by default -- without touching task_struct or
exit.c. The only behavioural delta versus upstream is that a user
task that has already cleared its mm in exit_mm() (a dying/zombie
task) now also requires CAP_SYS_PTRACE to attach, instead of being
remembered as previously dumpable. Such targets are rarely ptraced
in practice.
Verified to apply with `patch -p1 -F0` (no offset, no fuzz, no rejects)
against kernel-4.18.0-553.124.1.el8_10.
Reported-by: Qualys Security Advisory <qsa@qualys.com>
Signed-off-by: Andrew Lukoshko <alukoshko@almalinux.org>
---
kernel/ptrace.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -351,8 +351,11 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
smp_rmb();
mm = task->mm;
- if (mm &&
- ((get_dumpable(mm) != SUID_DUMP_USER) &&
- !ptrace_has_cap(mm->user_ns, mode)))
- return -EPERM;
+ if (mm) {
+ if ((get_dumpable(mm) != SUID_DUMP_USER) &&
+ !ptrace_has_cap(mm->user_ns, mode))
+ return -EPERM;
+ } else if (!ptrace_has_cap(&init_user_ns, mode)) {
+ return -EPERM;
+ }
return security_ptrace_access_check(task, mode);
--
2.43.0

9
SPECS/kernel.spec
View File

@ -38,11 +38,11 @@
# define buildid .local
%define specversion 4.18.0
%define pkgrelease 553.124.3.el8_10
%define pkgrelease 553.124.4.el8_10
%define tarfile_release 553.124.1.el8_10
# allow pkg_release to have configurable %%{?dist} tag
%define specrelease 553.124.3%{?dist}
%define specrelease 553.124.4%{?dist}
%define pkg_release %{specrelease}%{?buildid}
@ -540,6 +540,7 @@ Patch2006: 0006-Bring-back-deprecated-pci-ids-to-lpfc-driver.patch
Patch2007: 0007-Bring-back-deprecated-pci-ids-to-qla4xxx-driver.patch
Patch2008: 0008-Bring-back-deprecated-pci-ids-to-be2iscsi-driver.patch
Patch1100: 1100-net-skbuff-propagate-shared-frag-marker.patch
Patch1101: 1101-ptrace-require-cap-on-mm-less-task.patch
# END OF PATCH DEFINITIONS
@ -1118,6 +1119,7 @@ ApplyPatch 0006-Bring-back-deprecated-pci-ids-to-lpfc-driver.patch
ApplyPatch 0007-Bring-back-deprecated-pci-ids-to-qla4xxx-driver.patch
ApplyPatch 0008-Bring-back-deprecated-pci-ids-to-be2iscsi-driver.patch
ApplyPatch 1100-net-skbuff-propagate-shared-frag-marker.patch
ApplyPatch 1101-ptrace-require-cap-on-mm-less-task.patch
# END OF PATCH APPLICATIONS
@ -2716,6 +2718,9 @@ fi
#
#
%changelog
* Fri May 15 2026 Andrew Lukoshko <alukoshko@almalinux.org> - 4.18.0-553.124.4
- ptrace: require CAP_SYS_PTRACE when task has no mm (kABI-safe)
* Thu May 14 2026 Eduard Abdullin <eabdullin@almalinux.org> - 4.18.0-553.124.3
- net: skbuff: propagate shared-frag marker through frag-transfer helpers