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authorChris Metcalf <cmetcalf@tilera.com>2010-10-28 15:47:06 -0400
committerChris Metcalf <cmetcalf@tilera.com>2010-11-01 15:31:17 -0400
commit1deb9c5dfb179819ecdbf80a1d121e26c63caab3 (patch)
treec6f6ec6030eb22f094a65c07e63312758d079794 /arch
parent34a89d26bdc4ba46a406fa3842239e921c493d44 (diff)
downloadop-kernel-dev-1deb9c5dfb179819ecdbf80a1d121e26c63caab3.zip
op-kernel-dev-1deb9c5dfb179819ecdbf80a1d121e26c63caab3.tar.gz
arch/tile: don't allow user code to set the PL via ptrace or signal return
The kernel was allowing any component of the pt_regs to be updated either by signal handlers writing to the stack, or by processes writing via PTRACE_POKEUSR or PTRACE_SETREGS, which meant they could set their PL up from 0 to 1 and get access to kernel code and data (or, in practice, cause a kernel panic). We now always reset the ex1 field, allowing the user to set their ICS bit only. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/tile/kernel/ptrace.c39
-rw-r--r--arch/tile/kernel/signal.c3
2 files changed, 24 insertions, 18 deletions
diff --git a/arch/tile/kernel/ptrace.c b/arch/tile/kernel/ptrace.c
index 9cd2988..e92e405 100644
--- a/arch/tile/kernel/ptrace.c
+++ b/arch/tile/kernel/ptrace.c
@@ -50,10 +50,10 @@ long arch_ptrace(struct task_struct *child, long request,
{
unsigned long __user *datap = (long __user __force *)data;
unsigned long tmp;
- int i;
long ret = -EIO;
- unsigned long *childregs;
char *childreg;
+ struct pt_regs copyregs;
+ int ex1_offset;
switch (request) {
@@ -80,6 +80,16 @@ long arch_ptrace(struct task_struct *child, long request,
if (addr >= PTREGS_SIZE)
break;
childreg = (char *)task_pt_regs(child) + addr;
+
+ /* Guard against overwrites of the privilege level. */
+ ex1_offset = PTREGS_OFFSET_EX1;
+#if defined(CONFIG_COMPAT) && defined(__BIG_ENDIAN)
+ if (is_compat_task()) /* point at low word */
+ ex1_offset += sizeof(compat_long_t);
+#endif
+ if (addr == ex1_offset)
+ data = PL_ICS_EX1(USER_PL, EX1_ICS(data));
+
#ifdef CONFIG_COMPAT
if (is_compat_task()) {
if (addr & (sizeof(compat_long_t)-1))
@@ -96,26 +106,19 @@ long arch_ptrace(struct task_struct *child, long request,
break;
case PTRACE_GETREGS: /* Get all registers from the child. */
- if (!access_ok(VERIFY_WRITE, datap, PTREGS_SIZE))
- break;
- childregs = (long *)task_pt_regs(child);
- for (i = 0; i < sizeof(struct pt_regs)/sizeof(unsigned long);
- ++i) {
- ret = __put_user(childregs[i], &datap[i]);
- if (ret != 0)
- break;
+ if (copy_to_user(datap, task_pt_regs(child),
+ sizeof(struct pt_regs)) == 0) {
+ ret = 0;
}
break;
case PTRACE_SETREGS: /* Set all registers in the child. */
- if (!access_ok(VERIFY_READ, datap, PTREGS_SIZE))
- break;
- childregs = (long *)task_pt_regs(child);
- for (i = 0; i < sizeof(struct pt_regs)/sizeof(unsigned long);
- ++i) {
- ret = __get_user(childregs[i], &datap[i]);
- if (ret != 0)
- break;
+ if (copy_from_user(&copyregs, datap,
+ sizeof(struct pt_regs)) == 0) {
+ copyregs.ex1 =
+ PL_ICS_EX1(USER_PL, EX1_ICS(copyregs.ex1));
+ *task_pt_regs(child) = copyregs;
+ ret = 0;
}
break;
diff --git a/arch/tile/kernel/signal.c b/arch/tile/kernel/signal.c
index 704ce0b..687719d 100644
--- a/arch/tile/kernel/signal.c
+++ b/arch/tile/kernel/signal.c
@@ -71,6 +71,9 @@ int restore_sigcontext(struct pt_regs *regs,
for (i = 0; i < sizeof(struct pt_regs)/sizeof(long); ++i)
err |= __get_user(regs->regs[i], &sc->gregs[i]);
+ /* Ensure that the PL is always set to USER_PL. */
+ regs->ex1 = PL_ICS_EX1(USER_PL, EX1_ICS(regs->ex1));
+
regs->faultnum = INT_SWINT_1_SIGRETURN;
err |= __get_user(*pr0, &sc->gregs[0]);
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