Messages in this thread Patch in this message | | | From | Josh Poimboeuf <> | Subject | [PATCH v4 51/57] x86/unwind: warn if stack grows up | Date | Thu, 18 Aug 2016 08:06:31 -0500 |
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Add a sanity check to ensure the stack only grows down, and print a warning if the check fails.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> --- arch/x86/kernel/unwind_frame.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c index 4dbdf4f..140dac4 100644 --- a/arch/x86/kernel/unwind_frame.c +++ b/arch/x86/kernel/unwind_frame.c @@ -32,6 +32,15 @@ unsigned long unwind_get_return_address(struct unwind_state *state) } EXPORT_SYMBOL_GPL(unwind_get_return_address); +static size_t regs_size(struct pt_regs *regs) +{ + /* x86_32 regs from kernel mode are two words shorter */ + if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs)) + return sizeof(*regs) - (2*sizeof(long)); + + return sizeof(*regs); +} + static bool is_last_task_frame(struct unwind_state *state) { unsigned long bp = (unsigned long)state->bp; @@ -86,6 +95,7 @@ bool unwind_next_frame(struct unwind_state *state) struct pt_regs *regs; unsigned long *next_bp, *next_frame; size_t next_len; + enum stack_type prev_type = state->stack_info.type; if (unwind_done(state)) return false; @@ -149,6 +159,18 @@ bool unwind_next_frame(struct unwind_state *state) goto bad_address; } + /* make sure it only unwinds up and doesn't overlap the last frame */ + if (state->stack_info.type == prev_type) { + if (state->regs && + (void *)next_frame < (void *)state->regs + + regs_size(state->regs)) + goto bad_address; + + if (state->bp && + (void *)next_frame < (void *)state->bp + FRAME_HEADER_SIZE) + goto bad_address; + } + /* move to the next frame */ if (regs) { state->regs = regs; @@ -165,12 +187,12 @@ bad_address: printk_deferred_once(KERN_WARNING "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n", state->regs, state->task->comm, - state->task->pid, next_bp); + state->task->pid, next_frame); else printk_deferred_once(KERN_WARNING "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n", state->bp, state->task->comm, - state->task->pid, next_bp); + state->task->pid, next_frame); the_end: state->stack_info.type = STACK_TYPE_UNKNOWN; return false; -- 2.7.4
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