This patch adds SROP mitigation logic to the powerpc signal delivery and sigreturn code. The cookie is placed in the sigframe just after (at a lower address) the ABI gap.
This is derived from the x86 SROP mitigation patch: https://lkml.org/lkml/2016/3/29/791. Signed-off-by: Rashmica Gupta <rashm...@gmail.com> --- arch/powerpc/kernel/signal_32.c | 33 +++++++++++++++++++++++++++++---- arch/powerpc/kernel/signal_64.c | 21 +++++++++++++++++++-- 2 files changed, 48 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c index b6aa378aff63..01e6d0c966ee 100644 --- a/arch/powerpc/kernel/signal_32.c +++ b/arch/powerpc/kernel/signal_32.c @@ -207,6 +207,7 @@ static inline int restore_general_regs(struct pt_regs *regs, * When we have signals to deliver, we set up on the * user stack, going down from the original stack pointer: * an ABI gap of 56 words + * a cookie * an mcontext struct * a sigcontext struct * a gap of __SIGNAL_FRAMESIZE bytes @@ -222,6 +223,7 @@ struct sigframe { struct sigcontext sctx_transact; struct mcontext mctx_transact; #endif + unsigned long user_cookie; /* * Programs using the rs6000/xcoff abi can save up to 19 gp * regs and 18 fp regs below sp before decrementing it. @@ -235,7 +237,7 @@ struct sigframe { /* * When we have rt signals to deliver, we set up on the * user stack, going down from the original stack pointer: - * one rt_sigframe struct (siginfo + ucontext + ABI gap) + * one rt_sigframe struct (siginfo + ucontext + cookie + ABI gap) * a gap of __SIGNAL_FRAMESIZE+16 bytes * (the +16 is to get the siginfo and ucontext in the same * positions as in older kernels). @@ -253,6 +255,7 @@ struct rt_sigframe { #ifdef CONFIG_PPC_TRANSACTIONAL_MEM struct ucontext uc_transact; #endif + unsigned long user_cookie; /* * Programs using the rs6000/xcoff abi can save up to 19 gp * regs and 18 fp regs below sp before decrementing it. @@ -980,11 +983,12 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset, unsigned long newsp = 0; int sigret; unsigned long tramp; - + void __user *cookie_location; /* Set up Signal Frame */ /* Put a Real Time Context onto stack */ rt_sf = get_sigframe(ksig, get_tm_stackpointer(regs), sizeof(*rt_sf), 1); addr = rt_sf; + cookie_location = &(rt_sf->user_cookie); if (unlikely(rt_sf == NULL)) goto badframe; @@ -1016,6 +1020,8 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset, __put_user((unsigned long)tm_frame, &rt_sf->uc_transact.uc_regs)) goto badframe; + if (set_sigcookie(cookie_location)) + goto badframe; if (save_tm_user_regs(regs, frame, tm_frame, sigret)) goto badframe; } @@ -1024,6 +1030,8 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset, { if (__put_user(0, &rt_sf->uc.uc_link)) goto badframe; + if (set_sigcookie(cookie_location)) + goto badframe; if (save_user_regs(regs, frame, tm_frame, sigret, 1)) goto badframe; } @@ -1219,11 +1227,13 @@ long sys_rt_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8, unsigned long tmp; int tm_restore = 0; #endif + void __user *user_cookie; /* Always make any pending restarted system calls return -EINTR */ current->restart_block.fn = do_no_restart_syscall; rt_sf = (struct rt_sigframe __user *) (regs->gpr[1] + __SIGNAL_FRAMESIZE + 16); + user_cookie = &(rt_sf->user_cookie); if (!access_ok(VERIFY_READ, rt_sf, sizeof(*rt_sf))) goto bad; #ifdef CONFIG_PPC_TRANSACTIONAL_MEM @@ -1264,6 +1274,9 @@ long sys_rt_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8, * always done it up until now so it is probably better not to * change it. -- paulus */ + + if (verify_clear_sigcookie(user_cookie)) + goto bad; #ifdef CONFIG_PPC64 if (compat_restore_altstack(&rt_sf->uc.uc_stack)) goto bad; @@ -1404,11 +1417,12 @@ int handle_signal32(struct ksignal *ksig, sigset_t *oldset, struct pt_regs *regs unsigned long newsp = 0; int sigret; unsigned long tramp; - + void __user *cookie_location; /* Set up Signal Frame */ frame = get_sigframe(ksig, get_tm_stackpointer(regs), sizeof(*frame), 1); if (unlikely(frame == NULL)) goto badframe; + cookie_location = &(frame->user_cookie); sc = (struct sigcontext __user *) &frame->sctx; #if _NSIG != 64 @@ -1436,6 +1450,8 @@ int handle_signal32(struct ksignal *ksig, sigset_t *oldset, struct pt_regs *regs #ifdef CONFIG_PPC_TRANSACTIONAL_MEM tm_mctx = &frame->mctx_transact; if (MSR_TM_ACTIVE(regs->msr)) { + if (set_sigcookie(cookie_location)) + goto badframe; if (save_tm_user_regs(regs, &frame->mctx, &frame->mctx_transact, sigret)) goto badframe; @@ -1443,6 +1459,8 @@ int handle_signal32(struct ksignal *ksig, sigset_t *oldset, struct pt_regs *regs else #endif { + if (set_sigcookie(cookie_location)) + goto badframe; if (save_user_regs(regs, &frame->mctx, tm_mctx, sigret, 1)) goto badframe; } @@ -1491,11 +1509,12 @@ long sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8, struct mcontext __user *mcp, *tm_mcp; unsigned long msr_hi; #endif - + void __user *user_cookie; /* Always make any pending restarted system calls return -EINTR */ current->restart_block.fn = do_no_restart_syscall; sf = (struct sigframe __user *)(regs->gpr[1] + __SIGNAL_FRAMESIZE); + user_cookie = &(sf->user_cookie); sc = &sf->sctx; addr = sc; if (copy_from_user(&sigctx, sc, sizeof(sigctx))) @@ -1521,13 +1540,19 @@ long sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8, if (MSR_TM_ACTIVE(msr_hi<<32)) { if (!cpu_has_feature(CPU_FTR_TM)) goto badframe; + if (verify_clear_sigcookie(user_cookie)) + goto badframe; if (restore_tm_user_regs(regs, mcp, tm_mcp)) goto badframe; } else #endif { + sr = (struct mcontext __user *)from_user_ptr(sigctx.regs); addr = sr; + if (verify_clear_sigcookie(user_cookie)) + goto badframe; + if (!access_ok(VERIFY_READ, sr, sizeof(*sr)) || restore_user_regs(regs, sr, 1)) goto badframe; diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c index 25520794aa37..0b6e3f61a59d 100644 --- a/arch/powerpc/kernel/signal_64.c +++ b/arch/powerpc/kernel/signal_64.c @@ -24,6 +24,7 @@ #include <linux/elf.h> #include <linux/ptrace.h> #include <linux/ratelimit.h> +#include <linux/signal.h> #include <asm/sigcontext.h> #include <asm/ucontext.h> @@ -35,6 +36,7 @@ #include <asm/vdso.h> #include <asm/switch_to.h> #include <asm/tm.h> +#include <asm/compat.h> #include "signal.h" @@ -48,7 +50,7 @@ /* * When we have signals to deliver, we set up on the user stack, * going down from the original stack pointer: - * 1) a rt_sigframe struct which contains the ucontext + * 1) a rt_sigframe struct which contains the ucontext. * 2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller * frame for the signal handler. */ @@ -64,6 +66,7 @@ struct rt_sigframe { struct siginfo __user *pinfo; void __user *puc; struct siginfo info; + unsigned long user_cookie; /* New 64 bit little-endian ABI allows redzone of 512 bytes below sp */ char abigap[USER_REDZONE_SIZE]; } __attribute__ ((aligned (16))); @@ -661,6 +664,10 @@ int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5, #ifdef CONFIG_PPC_TRANSACTIONAL_MEM unsigned long msr; #endif + /* Only need the sigframe to get the cookie */ + struct rt_sigframe __user *sf = (struct rt_sigframe __user + *)regs->gpr[1]; + void __user *user_cookie = &(sf->user_cookie); /* Always make any pending restarted system calls return -EINTR */ current->restart_block.fn = do_no_restart_syscall; @@ -682,13 +689,16 @@ int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5, if (restore_tm_sigcontexts(regs, &uc->uc_mcontext, &uc_transact->uc_mcontext)) goto badframe; + if (verify_clear_sigcookie(user_cookie)) + goto badframe; } else /* Fall through, for non-TM restore */ #endif if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext)) goto badframe; - + if (verify_clear_sigcookie(user_cookie)) + goto badframe; if (restore_altstack(&uc->uc_stack)) goto badframe; @@ -710,6 +720,7 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs struct rt_sigframe __user *frame; unsigned long newsp = 0; long err = 0; + void __user *cookie_location; frame = get_sigframe(ksig, get_tm_stackpointer(regs), sizeof(*frame), 0); if (unlikely(frame == NULL)) @@ -724,12 +735,17 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs /* Create the ucontext. */ err |= __put_user(0, &frame->uc.uc_flags); err |= __save_altstack(&frame->uc.uc_stack, regs->gpr[1]); + + cookie_location = &(frame->user_cookie); #ifdef CONFIG_PPC_TRANSACTIONAL_MEM if (MSR_TM_ACTIVE(regs->msr)) { /* The ucontext_t passed to userland points to the second * ucontext_t (for transactional state) with its uc_link ptr. */ err |= __put_user(&frame->uc_transact, &frame->uc.uc_link); + + err |= set_sigcookie(cookie_location); + err |= setup_tm_sigcontexts(&frame->uc.uc_mcontext, &frame->uc_transact.uc_mcontext, regs, ksig->sig, @@ -739,6 +755,7 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs #endif { err |= __put_user(0, &frame->uc.uc_link); + err |= set_sigcookie(cookie_location); err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, ksig->sig, NULL, (unsigned long)ksig->ka.sa.sa_handler, 1); -- 2.5.0 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
