+ i386-fix-recursive-faults-during-oops-when-current.patch added to -mm tree

[akpm@xxxxxxxx]

The patch titled

     i386: fix recursive faults during oops when current is invalid

has been added to the -mm tree.  Its filename is

     i386-fix-recursive-faults-during-oops-when-current.patch

See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this

------------------------------------------------------
Subject: i386: fix recursive faults during oops when current is invalid
From: Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx>

Fix recursive faults during oops caused by invalid value in current by
using __get_user()/__put_user() when dereferencing it.

Reported by Krzysztof Halasa <khc@xxxxxxxxx>

Signed-off-by: Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---

 arch/i386/kernel/traps.c |   18 ++++++++++++++----
 arch/i386/mm/fault.c     |    7 ++++---
 2 files changed, 18 insertions(+), 7 deletions(-)

diff -puN arch/i386/kernel/traps.c~i386-fix-recursive-faults-during-oops-when-current arch/i386/kernel/traps.c
--- a/arch/i386/kernel/traps.c~i386-fix-recursive-faults-during-oops-when-current
+++ a/arch/i386/kernel/traps.c
@@ -278,8 +278,16 @@ void show_registers(struct pt_regs *regs
 	int i;
 	int in_kernel = 1;
 	unsigned long esp;
+	char *comm = "<bad task>";
+	pid_t pid = 0;
+	void *thread_info = 0;
 	unsigned short ss;
 
+	__get_user(thread_info, &current->thread_info);
+	__get_user(pid, &current->pid);
+	if (!__get_user(comm, (char **)current->comm))
+		comm = current->comm;
+
 	esp = (unsigned long) (&regs->esp);
 	savesegment(ss, ss);
 	if (user_mode_vm(regs)) {
@@ -302,8 +310,8 @@ void show_registers(struct pt_regs *regs
 	printk(KERN_EMERG "ds: %04x   es: %04x   ss: %04x\n",
 		regs->xds & 0xffff, regs->xes & 0xffff, ss);
 	printk(KERN_EMERG "Process %.*s (pid: %d, ti=%p task=%p task.ti=%p)",
-		TASK_COMM_LEN, current->comm, current->pid,
-		current_thread_info(), current, current->thread_info);
+		TASK_COMM_LEN, comm, pid,
+		current_thread_info(), current, thread_info);
 	/*
 	 * When in-kernel, we also print out the stack and code at the
 	 * time of the fault..
@@ -382,6 +390,7 @@ void die(const char * str, struct pt_reg
 	};
 	static int die_counter;
 	unsigned long flags;
+	unsigned long trap_no = 0; /* default if task pointer is corrupt */
 
 	oops_enter();
 
@@ -414,8 +423,9 @@ void die(const char * str, struct pt_reg
 #endif
 		printk("\n");
 		sysfs_printk_last_file();
-		if (notify_die(DIE_OOPS, str, regs, err,
-			    current->thread.trap_no, SIGSEGV) != NOTIFY_STOP) {
+		__get_user(trap_no, &current->thread.trap_no);
+		if (notify_die(DIE_OOPS, str, regs, err, trap_no, SIGSEGV) !=
+				NOTIFY_STOP) {
 			show_registers(regs);
 			/* Executive summary in case the oops scrolled away */
 			esp = (unsigned long) (&regs->esp);
diff -puN arch/i386/mm/fault.c~i386-fix-recursive-faults-during-oops-when-current arch/i386/mm/fault.c
--- a/arch/i386/mm/fault.c~i386-fix-recursive-faults-during-oops-when-current
+++ a/arch/i386/mm/fault.c
@@ -585,9 +585,10 @@ no_context:
 		printk(KERN_ALERT "*pte = %08lx\n", page);
 	}
 #endif
-	tsk->thread.cr2 = address;
-	tsk->thread.trap_no = 14;
-	tsk->thread.error_code = error_code;
+	/* avoid possible fault here if tsk is garbage */
+	__put_user(address, &tsk->thread.cr2);
+	__put_user(14, &tsk->thread.trap_no);
+	__put_user(error_code, &tsk->thread.error_code);
 	die("Oops", regs, error_code);
 	bust_spinlocks(0);
 	do_exit(SIGKILL);
_

Patches currently in -mm which might be from 76306.1226@xxxxxxxxxxxxxx are

ieee80211-tkip-requires-crc32.patch
i386-print-stack-size-in-oops-messages.patch
sleazy-fpu-feature-i386-support.patch
i386-early-fault-handler.patch
i386-fix-recursive-faults-during-oops-when-current.patch

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