| Message ID | 20140801030520.GA27665@mew (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Aug 01, 2014 at 04:05:20AM +0100, Omar Sandoval wrote: > The kgdb breakpoint hooks (kgdb_brk_fn and kgdb_compiled_brk_fn) should only be > entered when a kgdb break instruction is executed from the kernel. Otherwise, > if kgdb is enabled, a userspace program can cause the kernel to drop into the > debugger by executing either KGDB_BREAKINST or KGDB_COMPILED_BREAK. > > Signed-off-by: Omar Sandoval <osandov@osandov.com> > --- > On a kernel running with kgdb enabled, this program reproduces the problem: > .globl _start > _start: > udf #65006 @ KGDB_BREAKINST > > The same problem has been fixed in ARM64. > > arch/arm/kernel/kgdb.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c > index 778c2f7..a74b53c 100644 > --- a/arch/arm/kernel/kgdb.c > +++ b/arch/arm/kernel/kgdb.c > @@ -160,12 +160,16 @@ static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr) > static struct undef_hook kgdb_brkpt_hook = { > .instr_mask = 0xffffffff, > .instr_val = KGDB_BREAKINST, > + .cpsr_mask = MODE_MASK, > + .cpsr_val = SVC_MODE, > .fn = kgdb_brk_fn > }; > > static struct undef_hook kgdb_compiled_brkpt_hook = { > .instr_mask = 0xffffffff, > .instr_val = KGDB_COMPILED_BREAK, > + .cpsr_mask = MODE_MASK, > + .cpsr_val = SVC_MODE, > .fn = kgdb_compiled_brk_fn > }; Acked-by: Will Deacon <will.deacon@arm.com> Please put this into rmk's patch system. Cheers, Will
diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c index 778c2f7..a74b53c 100644 --- a/arch/arm/kernel/kgdb.c +++ b/arch/arm/kernel/kgdb.c @@ -160,12 +160,16 @@ static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr) static struct undef_hook kgdb_brkpt_hook = { .instr_mask = 0xffffffff, .instr_val = KGDB_BREAKINST, + .cpsr_mask = MODE_MASK, + .cpsr_val = SVC_MODE, .fn = kgdb_brk_fn }; static struct undef_hook kgdb_compiled_brkpt_hook = { .instr_mask = 0xffffffff, .instr_val = KGDB_COMPILED_BREAK, + .cpsr_mask = MODE_MASK, + .cpsr_val = SVC_MODE, .fn = kgdb_compiled_brk_fn };
The kgdb breakpoint hooks (kgdb_brk_fn and kgdb_compiled_brk_fn) should only be entered when a kgdb break instruction is executed from the kernel. Otherwise, if kgdb is enabled, a userspace program can cause the kernel to drop into the debugger by executing either KGDB_BREAKINST or KGDB_COMPILED_BREAK. Signed-off-by: Omar Sandoval <osandov@osandov.com> --- On a kernel running with kgdb enabled, this program reproduces the problem: .globl _start _start: udf #65006 @ KGDB_BREAKINST The same problem has been fixed in ARM64. arch/arm/kernel/kgdb.c | 4 ++++ 1 file changed, 4 insertions(+)