[PATCH v5 5/6] prctl: Allow checkpoint/restore capable processes to change exe link
From: Adrian Reber <hidden>
Date: 2020-07-15 14:53:08
Also in:
linux-fsdevel, lkml, selinux
Subsystem:
the rest · Maintainer:
Linus Torvalds
From: Nicolas Viennot <redacted> Allow CAP_CHECKPOINT_RESTORE capable users to change /proc/self/exe. This commit also changes the permission error code from -EINVAL to -EPERM for consistency with the rest of the prctl() syscall when checking capabilities. Signed-off-by: Nicolas Viennot <redacted> Signed-off-by: Adrian Reber <redacted> --- kernel/sys.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/kernel/sys.c b/kernel/sys.c
index 00a96746e28a..dd59b9142b1d 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c@@ -2007,12 +2007,14 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data if (prctl_map.exe_fd != (u32)-1) { /* - * Make sure the caller has the rights to - * change /proc/pid/exe link: only local sys admin should - * be allowed to. + * Check if the current user is checkpoint/restore capable. + * At the time of this writing, it checks for CAP_SYS_ADMIN + * or CAP_CHECKPOINT_RESTORE. + * Note that a user with access to ptrace can masquerade an + * arbitrary program as any executable, even setuid ones. */ - if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN)) - return -EINVAL; + if (!checkpoint_restore_ns_capable(current_user_ns())) + return -EPERM; error = prctl_set_mm_exe_file(mm, prctl_map.exe_fd); if (error)
--
2.26.2