From ed79b86d8acf1f3d3bb83f04dc216c8dfa1d5970 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Thu, 20 Nov 2008 10:54:09 +0100 Subject: [PATCH] parisc: fix bug in compat_arch_ptrace Commit 81e192d6ce303b6792aa38ff35f41a1a7357f23a ("parisc: convert to generic compat_sys_ptrace") introduced a bug which segfaults the parisc 64bit kernel when stracing 32bit applications: Kernel Fault: Code=15 regs=00000000bafa42b0 (Addr=00000001baf5ab57) YZrvWESTHLNXBCVMcbcbcbcbOGFRQPDI PSW: 00001000000001101111111100001011 Tainted: G W r00-03 000000ff0806ff0b 000000004068edc0 00000000401203f8 00000000fb3e2508 r04-07 0000000040686dc0 00000000baf5a800 fffffffffffffffc fffffffffb3e2508 r08-11 00000000baf5a800 000000000004b068 00000000000402b0 0000000000040d68 r12-15 0000000000042a9c 0000000000040a9c 0000000000040d60 0000000000042e9c r16-19 000000000004b060 000000000004b058 0000000000042d9c ffffffffffffffff r20-23 000000000800000b 0000000000000000 000000000800000b fffffffffb3e2508 r24-27 00000000fffffffc 0000000000000003 00000000fffffffc 0000000040686dc0 r28-31 00000001baf5a7ff 00000000bafa4280 00000000bafa42b0 00000000000001d7 sr00-03 0000000000fca000 0000000000000000 0000000000000000 0000000000fca000 sr04-07 0000000000000000 0000000000000000 0000000000000000 0000000000000000 IASQ: 0000000000000000 0000000000000000 IAOQ: 0000000040120400 0000000040120404 IIR: 4b9a06b0 ISR: 0000000000000000 IOR: 00000001baf5ab57 CPU: 0 CR30: 00000000bafa4000 CR31: 00000000d22344e0 ORIG_R28: 00000000fb3e2248 IAOQ[0]: compat_arch_ptrace+0xb8/0x160 IAOQ[1]: compat_arch_ptrace+0xbc/0x160 RP(r2): compat_arch_ptrace+0xb0/0x160 Backtrace: [<00000000401612ac>] compat_sys_ptrace+0x15c/0x180 [<0000000040104ef8>] syscall_exit+0x0/0x14 The problem is that compat_arch_ptrace() enters with an addr value of type compat_ulong_t and calls translate_usr_offset() to translate the address offset into a struct pt_regs offset like this: addr = translate_usr_offset(addr) this means that any return value of translate_usr_offset() is stored back as compat_ulong_t type into the addr variable. But since translate_usr_offset() returns -1 for invalid offsets, addr can now get the value 0xffffffff which then fails the next return-value sanity check and thus the kernel tries to access invalid memory: if (addr < 0) break; Fix this bug by modifying translate_usr_offset() to take and return values of type compat_ulong_t, and by returning the value "sizeof(struct pt_regs)" as an error indicator. Additionally change the sanity check to check for return values for >= sizeof(struct pt_regs). This patch survived my compile and run-tests. Signed-off-by: Helge Deller Signed-off-by: Linus Torvalds --- arch/parisc/kernel/ptrace.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/parisc/kernel/ptrace.c b/arch/parisc/kernel/ptrace.c index 90904f9dfc5..927db3668b6 100644 --- a/arch/parisc/kernel/ptrace.c +++ b/arch/parisc/kernel/ptrace.c @@ -183,10 +183,10 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data) * being 64 bit in both cases. */ -static long translate_usr_offset(long offset) +static compat_ulong_t translate_usr_offset(compat_ulong_t offset) { if (offset < 0) - return -1; + return sizeof(struct pt_regs); else if (offset <= 32*4) /* gr[0..31] */ return offset * 2 + 4; else if (offset <= 32*4+32*8) /* gr[0..31] + fr[0..31] */ @@ -194,7 +194,7 @@ static long translate_usr_offset(long offset) else if (offset < sizeof(struct pt_regs)/2 + 32*4) return offset * 2 + 4 - 32*8; else - return -1; + return sizeof(struct pt_regs); } long compat_arch_ptrace(struct task_struct *child, compat_long_t request, @@ -209,7 +209,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request, if (addr & (sizeof(compat_uint_t)-1)) break; addr = translate_usr_offset(addr); - if (addr < 0) + if (addr >= sizeof(struct pt_regs)) break; tmp = *(compat_uint_t *) ((char *) task_regs(child) + addr); @@ -236,7 +236,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request, if (addr & (sizeof(compat_uint_t)-1)) break; addr = translate_usr_offset(addr); - if (addr < 0) + if (addr >= sizeof(struct pt_regs)) break; if (addr >= PT_FR0 && addr <= PT_FR31 + 4) { /* Special case, fp regs are 64 bits anyway */ -- 2.41.0