Hi there, When running a 31-bit ptrace, on either an s390 or s390x kernel, reads and writes into a padding area in struct user_regs_struct32 will result in a kernel panic. This is also known as CVE-2008-1514. Test case available here: http://sources.redhat.com/cgi-bin/cvsweb.cgi/~checkout~/tests/ptrace-tests/tests/user-area-padding.c?cvsroot=systemtap Steps to reproduce: 1) wget the above 2) gcc -o user-area-padding-31bit user-area-padding.c -Wall -ggdb2 -D_GNU_SOURCE -m31 3) ./user-area-padding-31bit <panic> Test status ----------- Without patch, both s390 and s390x kernels panic. With patch, the test case, as well as the gdb testsuite, pass without incident, padding area reads returning zero, writes ignored. Nb: original version returned -EINVAL on write attempts, which broke the gdb test and made the test case slightly unhappy, Jan Kratochvil suggested the change to return 0 on write attempts. Signed-off-by: Jarod Wilson <jarod@xxxxxxxxxx> Tested-by: Jan Kratochvil <jan.kratochvil@xxxxxxxxxx> --- arch/s390/kernel/compat_ptrace.h | 1 + arch/s390/kernel/ptrace.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 29 insertions(+), 0 deletions(-) diff --git a/arch/s390/kernel/compat_ptrace.h b/arch/s390/kernel/compat_ptrace.h index cde81fa..a2be3a9 100644 --- a/arch/s390/kernel/compat_ptrace.h +++ b/arch/s390/kernel/compat_ptrace.h @@ -42,6 +42,7 @@ struct user_regs_struct32 u32 gprs[NUM_GPRS]; u32 acrs[NUM_ACRS]; u32 orig_gpr2; + /* nb: there's a 4-byte hole here */ s390_fp_regs fp_regs; /* * These per registers are in here so that gdb can modify them diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c index 2815bfe..d00e403 100644 --- a/arch/s390/kernel/ptrace.c +++ b/arch/s390/kernel/ptrace.c @@ -170,6 +170,13 @@ static unsigned long __peek_user(struct task_struct *child, addr_t addr) */ tmp = (addr_t) task_pt_regs(child)->orig_gpr2; + } else if (addr < (addr_t) &dummy->regs.fp_regs) { + /* + * prevent reads of padding hole between + * orig_gpr2 and fp_regs on s390. + */ + tmp = 0; + } else if (addr < (addr_t) (&dummy->regs.fp_regs + 1)) { /* * floating point regs. are stored in the thread structure @@ -270,6 +277,13 @@ static int __poke_user(struct task_struct *child, addr_t addr, addr_t data) */ task_pt_regs(child)->orig_gpr2 = data; + } else if (addr < (addr_t) &dummy->regs.fp_regs) { + /* + * prevent writes of padding hole between + * orig_gpr2 and fp_regs on s390. + */ + return 0; + } else if (addr < (addr_t) (&dummy->regs.fp_regs + 1)) { /* * floating point regs. are stored in the thread structure @@ -428,6 +442,13 @@ static u32 __peek_user_compat(struct task_struct *child, addr_t addr) */ tmp = *(__u32*)((addr_t) &task_pt_regs(child)->orig_gpr2 + 4); + } else if (addr < (addr_t) &dummy->regs.fp_regs) { + /* + * prevent reads of padding hole between + * orig_gpr2 and fp_regs on s390. + */ + tmp = 0; + } else if (addr < (addr_t) (&dummy32->regs.fp_regs + 1)) { /* * floating point regs. are stored in the thread structure @@ -514,6 +535,13 @@ static int __poke_user_compat(struct task_struct *child, */ *(__u32*)((addr_t) &task_pt_regs(child)->orig_gpr2 + 4) = tmp; + } else if (addr < (addr_t) &dummy->regs.fp_regs) { + /* + * prevent writess of padding hole between + * orig_gpr2 and fp_regs on s390. + */ + return 0; + } else if (addr < (addr_t) (&dummy32->regs.fp_regs + 1)) { /* * floating point regs. are stored in the thread structure -- Jarod Wilson jarod@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
