Home Home > GIT Browse
summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorWill Drewry <wad@chromium.org>2012-07-13 12:06:35 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-13 14:25:55 -0700
commit5651721edec25bf73cee060150e684044eac42dc (patch)
treedc43e7c23455cd61fa2bafad7faffe45b44d6885
parentac7d181e323a888015e19e2e4d776095a0433787 (diff)
x86/vsyscall: allow seccomp filter in vsyscall=emulate
If a seccomp filter program is installed, older static binaries and distributions with older libc implementations (glibc 2.13 and earlier) that rely on vsyscall use will be terminated regardless of the filter program policy when executing time, gettimeofday, or getcpu. This is only the case when vsyscall emulation is in use (vsyscall=emulate is the default). This patch emulates system call entry inside a vsyscall=emulate by populating regs->ax and regs->orig_ax with the system call number prior to calling into seccomp such that all seccomp-dependencies function normally. Additionally, system call return behavior is emulated in line with other vsyscall entrypoints for the trace/trap cases. [ v2: fixed ip and sp on SECCOMP_RET_TRAP/TRACE (thanks to luto@mit.edu) ] Reported-and-tested-by: Owen Kibel <qmewlo@gmail.com> Signed-off-by: Will Drewry <wad@chromium.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/x86/kernel/vsyscall_64.c35
1 files changed, 31 insertions, 4 deletions
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 7515cf0e1805..08a18d0dcc5a 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -139,6 +139,15 @@ static int addr_to_vsyscall_nr(unsigned long addr)
return nr;
}
+static int vsyscall_seccomp(struct task_struct *tsk, int syscall_nr)
+{
+ if (!seccomp_mode(&tsk->seccomp))
+ return 0;
+ task_pt_regs(tsk)->orig_ax = syscall_nr;
+ task_pt_regs(tsk)->ax = syscall_nr;
+ return __secure_computing(syscall_nr);
+}
+
static bool write_ok_or_segv(unsigned long ptr, size_t size)
{
/*
@@ -174,6 +183,7 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
int vsyscall_nr;
int prev_sig_on_uaccess_error;
long ret;
+ int skip;
/*
* No point in checking CS -- the only way to get here is a user mode
@@ -205,9 +215,6 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
}
tsk = current;
- if (seccomp_mode(&tsk->seccomp))
- do_exit(SIGKILL);
-
/*
* With a real vsyscall, page faults cause SIGSEGV. We want to
* preserve that behavior to make writing exploits harder.
@@ -222,8 +229,13 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
* address 0".
*/
ret = -EFAULT;
+ skip = 0;
switch (vsyscall_nr) {
case 0:
+ skip = vsyscall_seccomp(tsk, __NR_gettimeofday);
+ if (skip)
+ break;
+
if (!write_ok_or_segv(regs->di, sizeof(struct timeval)) ||
!write_ok_or_segv(regs->si, sizeof(struct timezone)))
break;
@@ -234,6 +246,10 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
break;
case 1:
+ skip = vsyscall_seccomp(tsk, __NR_time);
+ if (skip)
+ break;
+
if (!write_ok_or_segv(regs->di, sizeof(time_t)))
break;
@@ -241,6 +257,10 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
break;
case 2:
+ skip = vsyscall_seccomp(tsk, __NR_getcpu);
+ if (skip)
+ break;
+
if (!write_ok_or_segv(regs->di, sizeof(unsigned)) ||
!write_ok_or_segv(regs->si, sizeof(unsigned)))
break;
@@ -253,6 +273,12 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
current_thread_info()->sig_on_uaccess_error = prev_sig_on_uaccess_error;
+ if (skip) {
+ if ((long)regs->ax <= 0L) /* seccomp errno emulation */
+ goto do_ret;
+ goto done; /* seccomp trace/trap */
+ }
+
if (ret == -EFAULT) {
/* Bad news -- userspace fed a bad pointer to a vsyscall. */
warn_bad_vsyscall(KERN_INFO, regs,
@@ -271,10 +297,11 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
regs->ax = ret;
+do_ret:
/* Emulate a ret instruction. */
regs->ip = caller;
regs->sp += 8;
-
+done:
return true;
sigsegv: