From: Jim Keniston Date: Wed, 23 Nov 2005 21:37:42 +0000 (-0800) Subject: [PATCH] kprobes: Fix return probes on sys_execve X-Git-Tag: v2.6.15-rc3~76 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8bf1101bd52573e0573e374d56d2feecdbb5e444;p=linux-2.6 [PATCH] kprobes: Fix return probes on sys_execve Fix a bug in kprobes that can cause an Oops or even a crash when a return probe is installed on one of the following functions: sys_execve, do_execve, load_*_binary, flush_old_exec, or flush_thread. The fix is to remove the call to kprobe_flush_task() in flush_thread(). This fix has been tested on all architectures for which the return-probes feature has been implemented (i386, x86_64, ppc64, ia64). Please apply. BACKGROUND Up to now, we have called kprobe_flush_task() under two situations: when a task exits, and when it execs. Flushing kretprobe_instances on exit is correct because (a) do_exit() doesn't return, and (b) one or more return-probed functions may be active when a task calls do_exit(). Neither is the case for sys_execve() and its callees. Initially, the mistaken call to kprobe_flush_task() on exec was harmless because we put the "real" return address of each active probed function back in the stack, just to be safe, when we recycled its kretprobe_instance. When support for ppc64 and ia64 was added, this safety measure couldn't be employed, and was eventually dropped even for i386 and x86_64. sys_execve() and its callees were informally blacklisted for return probes until this fix was developed. Acked-by: Prasanna S Panchamukhi Signed-off-by: Jim Keniston Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c index 1cb261f225..df6c2bcde0 100644 --- a/arch/i386/kernel/process.c +++ b/arch/i386/kernel/process.c @@ -393,13 +393,6 @@ void flush_thread(void) { struct task_struct *tsk = current; - /* - * Remove function-return probe instances associated with this task - * and put them back on the free list. Do not insert an exit probe for - * this function, it will be disabled by kprobe_flush_task if you do. - */ - kprobe_flush_task(tsk); - memset(tsk->thread.debugreg, 0, sizeof(unsigned long)*8); memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array)); /* diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c index 4305d2ba76..2e33665d9c 100644 --- a/arch/ia64/kernel/process.c +++ b/arch/ia64/kernel/process.c @@ -718,13 +718,6 @@ kernel_thread_helper (int (*fn)(void *), void *arg) void flush_thread (void) { - /* - * Remove function-return probe instances associated with this task - * and put them back on the free list. Do not insert an exit probe for - * this function, it will be disabled by kprobe_flush_task if you do. - */ - kprobe_flush_task(current); - /* drop floating-point and debug-register state if it exists: */ current->thread.flags &= ~(IA64_THREAD_FPH_VALID | IA64_THREAD_DBG_VALID); ia64_drop_fpu(current); diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index de69fb37c7..a5a7542a8f 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -457,7 +457,6 @@ void flush_thread(void) if (t->flags & _TIF_ABI_PENDING) t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT); #endif - kprobe_flush_task(current); #ifndef CONFIG_SMP if (last_task_used_math == current) diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c index 5afd63e8ce..7519fc520e 100644 --- a/arch/x86_64/kernel/process.c +++ b/arch/x86_64/kernel/process.c @@ -351,13 +351,6 @@ void flush_thread(void) struct task_struct *tsk = current; struct thread_info *t = current_thread_info(); - /* - * Remove function-return probe instances associated with this task - * and put them back on the free list. Do not insert an exit probe for - * this function, it will be disabled by kprobe_flush_task if you do. - */ - kprobe_flush_task(tsk); - if (t->flags & _TIF_ABI_PENDING) t->flags ^= (_TIF_ABI_PENDING | _TIF_IA32);