diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2017-08-20 13:26:27 -0700 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2017-09-15 18:30:18 +0100 |
| commit | b5a16892623afec2d3212b963dd688b258002b4b (patch) | |
| tree | 3e6af25e7857a61348e79e846556ed11089175f1 | |
| parent | 32cb2d4a59d0512aa825e7f0352f66063482cc07 (diff) | |
Sanitize 'move_pages()' permission checks
commit 197e7e521384a23b9e585178f3f11c9fa08274b9 upstream.
The 'move_paghes()' system call was introduced long long ago with the
same permission checks as for sending a signal (except using
CAP_SYS_NICE instead of CAP_SYS_KILL for the overriding capability).
That turns out to not be a great choice - while the system call really
only moves physical page allocations around (and you need other
capabilities to do a lot of it), you can check the return value to map
out some the virtual address choices and defeat ASLR of a binary that
still shares your uid.
So change the access checks to the more common 'ptrace_may_access()'
model instead.
This tightens the access checks for the uid, and also effectively
changes the CAP_SYS_NICE check to CAP_SYS_PTRACE, but it's unlikely that
anybody really _uses_ this legacy system call any more (we hav ebetter
NUMA placement models these days), so I expect nobody to notice.
Famous last words.
Reported-by: Otto Ebeling <otto.ebeling@iki.fi>
Acked-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | mm/migrate.c | 11 |
1 files changed, 3 insertions, 8 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index 5193433d8605..4fb18030de62 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -38,6 +38,7 @@ #include <linux/gfp.h> #include <linux/balloon_compaction.h> #include <linux/mmu_notifier.h> +#include <linux/ptrace.h> #include <asm/tlbflush.h> @@ -1484,7 +1485,6 @@ SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, const int __user *, nodes, int __user *, status, int, flags) { - const struct cred *cred = current_cred(), *tcred; struct task_struct *task; struct mm_struct *mm; int err; @@ -1508,14 +1508,9 @@ SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, /* * Check if this process has the right to modify the specified - * process. The right exists if the process has administrative - * capabilities, superuser privileges or the same - * userid as the target process. + * process. Use the regular "ptrace_may_access()" checks. */ - tcred = __task_cred(task); - if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) && - !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) && - !capable(CAP_SYS_NICE)) { + if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { rcu_read_unlock(); err = -EPERM; goto out; |