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-rw-r--r--arch/arm64/kernel/signal.c92
1 files changed, 78 insertions, 14 deletions
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 561986947530..c7d311d8b92a 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -19,6 +19,7 @@
#include <linux/ratelimit.h>
#include <linux/rseq.h>
#include <linux/syscalls.h>
+#include <linux/pkeys.h>
#include <asm/daifflags.h>
#include <asm/debug-monitors.h>
@@ -66,10 +67,63 @@ struct rt_sigframe_user_layout {
unsigned long end_offset;
};
+/*
+ * Holds any EL0-controlled state that influences unprivileged memory accesses.
+ * This includes both accesses done in userspace and uaccess done in the kernel.
+ *
+ * This state needs to be carefully managed to ensure that it doesn't cause
+ * uaccess to fail when setting up the signal frame, and the signal handler
+ * itself also expects a well-defined state when entered.
+ */
+struct user_access_state {
+ u64 por_el0;
+};
+
#define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
#define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
#define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)
+/*
+ * Save the user access state into ua_state and reset it to disable any
+ * restrictions.
+ */
+static void save_reset_user_access_state(struct user_access_state *ua_state)
+{
+ if (system_supports_poe()) {
+ u64 por_enable_all = 0;
+
+ for (int pkey = 0; pkey < arch_max_pkey(); pkey++)
+ por_enable_all |= POE_RXW << (pkey * POR_BITS_PER_PKEY);
+
+ ua_state->por_el0 = read_sysreg_s(SYS_POR_EL0);
+ write_sysreg_s(por_enable_all, SYS_POR_EL0);
+ /* Ensure that any subsequent uaccess observes the updated value */
+ isb();
+ }
+}
+
+/*
+ * Set the user access state for invoking the signal handler.
+ *
+ * No uaccess should be done after that function is called.
+ */
+static void set_handler_user_access_state(void)
+{
+ if (system_supports_poe())
+ write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0);
+}
+
+/*
+ * Restore the user access state to the values saved in ua_state.
+ *
+ * No uaccess should be done after that function is called.
+ */
+static void restore_user_access_state(const struct user_access_state *ua_state)
+{
+ if (system_supports_poe())
+ write_sysreg_s(ua_state->por_el0, SYS_POR_EL0);
+}
+
static void init_user_layout(struct rt_sigframe_user_layout *user)
{
const size_t reserved_size =
@@ -261,18 +315,20 @@ static int restore_fpmr_context(struct user_ctxs *user)
return err;
}
-static int preserve_poe_context(struct poe_context __user *ctx)
+static int preserve_poe_context(struct poe_context __user *ctx,
+ const struct user_access_state *ua_state)
{
int err = 0;
__put_user_error(POE_MAGIC, &ctx->head.magic, err);
__put_user_error(sizeof(*ctx), &ctx->head.size, err);
- __put_user_error(read_sysreg_s(SYS_POR_EL0), &ctx->por_el0, err);
+ __put_user_error(ua_state->por_el0, &ctx->por_el0, err);
return err;
}
-static int restore_poe_context(struct user_ctxs *user)
+static int restore_poe_context(struct user_ctxs *user,
+ struct user_access_state *ua_state)
{
u64 por_el0;
int err = 0;
@@ -282,7 +338,7 @@ static int restore_poe_context(struct user_ctxs *user)
__get_user_error(por_el0, &(user->poe->por_el0), err);
if (!err)
- write_sysreg_s(por_el0, SYS_POR_EL0);
+ ua_state->por_el0 = por_el0;
return err;
}
@@ -850,7 +906,8 @@ invalid:
}
static int restore_sigframe(struct pt_regs *regs,
- struct rt_sigframe __user *sf)
+ struct rt_sigframe __user *sf,
+ struct user_access_state *ua_state)
{
sigset_t set;
int i, err;
@@ -899,7 +956,7 @@ static int restore_sigframe(struct pt_regs *regs,
err = restore_zt_context(&user);
if (err == 0 && system_supports_poe() && user.poe)
- err = restore_poe_context(&user);
+ err = restore_poe_context(&user, ua_state);
return err;
}
@@ -908,6 +965,7 @@ SYSCALL_DEFINE0(rt_sigreturn)
{
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe __user *frame;
+ struct user_access_state ua_state;
/* Always make any pending restarted system calls return -EINTR */
current->restart_block.fn = do_no_restart_syscall;
@@ -924,12 +982,14 @@ SYSCALL_DEFINE0(rt_sigreturn)
if (!access_ok(frame, sizeof (*frame)))
goto badframe;
- if (restore_sigframe(regs, frame))
+ if (restore_sigframe(regs, frame, &ua_state))
goto badframe;
if (restore_altstack(&frame->uc.uc_stack))
goto badframe;
+ restore_user_access_state(&ua_state);
+
return regs->regs[0];
badframe:
@@ -1035,7 +1095,8 @@ static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
}
static int setup_sigframe(struct rt_sigframe_user_layout *user,
- struct pt_regs *regs, sigset_t *set)
+ struct pt_regs *regs, sigset_t *set,
+ const struct user_access_state *ua_state)
{
int i, err = 0;
struct rt_sigframe __user *sf = user->sigframe;
@@ -1097,10 +1158,9 @@ static int setup_sigframe(struct rt_sigframe_user_layout *user,
struct poe_context __user *poe_ctx =
apply_user_offset(user, user->poe_offset);
- err |= preserve_poe_context(poe_ctx);
+ err |= preserve_poe_context(poe_ctx, ua_state);
}
-
/* ZA state if present */
if (system_supports_sme() && err == 0 && user->za_offset) {
struct za_context __user *za_ctx =
@@ -1237,9 +1297,6 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
sme_smstop();
}
- if (system_supports_poe())
- write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0);
-
if (ka->sa.sa_flags & SA_RESTORER)
sigtramp = ka->sa.sa_restorer;
else
@@ -1253,6 +1310,7 @@ static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
{
struct rt_sigframe_user_layout user;
struct rt_sigframe __user *frame;
+ struct user_access_state ua_state;
int err = 0;
fpsimd_signal_preserve_current_state();
@@ -1260,13 +1318,14 @@ static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
if (get_sigframe(&user, ksig, regs))
return 1;
+ save_reset_user_access_state(&ua_state);
frame = user.sigframe;
__put_user_error(0, &frame->uc.uc_flags, err);
__put_user_error(NULL, &frame->uc.uc_link, err);
err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
- err |= setup_sigframe(&user, regs, set);
+ err |= setup_sigframe(&user, regs, set, &ua_state);
if (err == 0) {
setup_return(regs, &ksig->ka, &user, usig);
if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
@@ -1276,6 +1335,11 @@ static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
}
}
+ if (err == 0)
+ set_handler_user_access_state();
+ else
+ restore_user_access_state(&ua_state);
+
return err;
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-03 11:41:12 +0100