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ARM: kgdb: ignore breakpoint instructions from user mode

Message ID 1373417259-22098-1-git-send-email-toddpoynor@google.com (mailing list archive)
State New, archived
Headers show

Commit Message

Todd Poynor July 10, 2013, 12:47 a.m. UTC 
Avoid conflicts with user mode usage of the same instructions, as with
Clang -ftrapv, and avoid a potential denial of service.

Signed-off-by: Todd Poynor <toddpoynor@google.com>
---
 arch/arm/kernel/kgdb.c | 4 ++++
 1 file changed, 4 insertions(+)
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Patch

diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c
index 778c2f7..b321c8f 100644
--- a/arch/arm/kernel/kgdb.c
+++ b/arch/arm/kernel/kgdb.c
@@ -144,6 +144,8 @@  int kgdb_arch_handle_exception(int exception_vector, int signo,
 
 static int kgdb_brk_fn(struct pt_regs *regs, unsigned int instr)
 {
+	if (user_mode(regs))
+		return -1;
 	kgdb_handle_exception(1, SIGTRAP, 0, regs);
 
 	return 0;
@@ -151,6 +153,8 @@  static int kgdb_brk_fn(struct pt_regs *regs, unsigned int instr)
 
 static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr)
 {
+	if (user_mode(regs))
+		return -1;
 	compiled_break = 1;
 	kgdb_handle_exception(1, SIGTRAP, 0, regs);