Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759989AbYCDI5X (ORCPT ); Tue, 4 Mar 2008 03:57:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753644AbYCDI5O (ORCPT ); Tue, 4 Mar 2008 03:57:14 -0500 Received: from e28smtp05.in.ibm.com ([59.145.155.5]:41964 "EHLO e28esmtp05.in.ibm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752193AbYCDI5N (ORCPT ); Tue, 4 Mar 2008 03:57:13 -0500 From: Srinivasa DS Organization: IBM To: Andrew Morton Subject: Re: [RFC] [PATCH] To refuse users from probing preempt_schedule() User-Agent: KMail/1.9.6 (enterprise 0.20071012.724442) Cc: linux-kernel@vger.kernel.org, ananth@in.ibm.com, Jim Keniston , srikar@linux.vnet.ibm.com References: <200802251127.40579.srinivasa@in.ibm.com> <20080304002521.2e67d7a5.akpm@linux-foundation.org> In-Reply-To: <20080304002521.2e67d7a5.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Disposition: inline Date: Tue, 4 Mar 2008 14:26:37 +0530 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200803041426.37293.srinivasa@in.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7439 Lines: 223 On Tuesday 04 March 2008 01:55:21 pm Andrew Morton wrote: > On Mon, 25 Feb 2008 11:27:40 +0530 srinivasa wrote: > > From: Srinivasa Ds > > > > This patch prohibits user from probing preempt_schedule(). One way of > > prohibiting the user from probing functions is by marking such > > functions with __kprobes. But this method doesn't work for those > > functions, which are already marked to different section like > > preempt_schedule() (belongs to __sched section). So we use blacklist > > approach to refuse user from probing these functions. > > > > In blacklist approach we populate the blacklisted function's starting > > address and its size in kprobe_blacklist structure. Then we verify the > > user specified address against start and end of the blacklisted function. > > So any attempt to register probe on blacklisted functions will be > > rejected. > > > > please let me know your comments. > > sparc64: > > kernel/kprobes.c: In function `in_kprobes_functions': > kernel/kprobes.c:516: error: `kprobe_blacklist' undeclared (first use in > this function) kernel/kprobes.c:516: error: (Each undeclared identifier is > reported only once kernel/kprobes.c:516: error: for each function it > appears in.) > kernel/kprobes.c: In function `init_kprobes': > kernel/kprobes.c:860: error: `kprobe_blacklist' undeclared (first use in > this function) > > > --- > > include/linux/kprobes.h | 7 ++++++ > > kernel/kprobes.c | 52 > > ++++++++++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 59 insertions(+) > > > > Index: linux-2.6.25-rc3/include/linux/kprobes.h > > =================================================================== > > --- linux-2.6.25-rc3.orig/include/linux/kprobes.h > > +++ linux-2.6.25-rc3/include/linux/kprobes.h > > @@ -173,6 +173,13 @@ struct kretprobe_blackpoint { > > const char *name; > > void *addr; > > }; > > + > > +struct kprobe_blackpoint { > > + const char *name; > > + unsigned long start_addr; > > + unsigned long range; > > +}; > > + > > I'm assuming that the placement of this definition inside > __ARCH_WANT_KPROBES_INSN_SLOT wqs accidental? Yes Andrew. Sorry I over looked __ARCH_WANT_KPROBES_INSN_SLOT and placed the struct kprobe_black_point in a wrong place. Patch, that you have attached below looks good, but for your reference, Iam attaching the modified patch below. > > --- a/kernel/kprobes.c~kprobes-prevent-probing-of-preempt_schedule-fix > +++ a/kernel/kprobes.c > @@ -72,6 +72,18 @@ DEFINE_MUTEX(kprobe_mutex); /* Protects > DEFINE_SPINLOCK(kretprobe_lock); /* Protects kretprobe_inst_table */ > static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL; > > +/* > + * Normally, functions that we'd want to prohibit kprobes in, are marked > + * __kprobes. But, there are cases where such functions already belong to > + * a different section (__sched for preempt_schedule) > + * > + * For such cases, we now have a blacklist > + */ > +struct kprobe_blackpoint kprobe_blacklist[] = { > + {"preempt_schedule",}, > + {NULL} /* Terminator */ > +}; > + > #ifdef __ARCH_WANT_KPROBES_INSN_SLOT > /* > * kprobe->ainsn.insn points to the copy of the instruction to be > @@ -89,18 +101,6 @@ struct kprobe_insn_page { > int ngarbage; > }; > > -/* > - * Normally, functions that we'd want to prohibit kprobes in, are marked > - * __kprobes. But, there are cases where such functions already belong to > - * a different section (__sched for preempt_schedule) > - * > - * For such cases, we now have a blacklist > - */ > -struct kprobe_blackpoint kprobe_blacklist[] = { > - {"preempt_schedule",}, > - {NULL} /* Terminator */ > -}; > - > enum kprobe_slot_state { > SLOT_CLEAN = 0, > SLOT_DIRTY = 1, > _ --- include/linux/kprobes.h | 7 ++++++ kernel/kprobes.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+) Index: linux-2.6.25-rc3/include/linux/kprobes.h =================================================================== --- linux-2.6.25-rc3.orig/include/linux/kprobes.h +++ linux-2.6.25-rc3/include/linux/kprobes.h @@ -173,6 +173,13 @@ struct kretprobe_blackpoint { const char *name; void *addr; }; + +struct kprobe_blackpoint { + const char *name; + unsigned long start_addr; + unsigned long range; +}; + extern struct kretprobe_blackpoint kretprobe_blacklist[]; static inline void kretprobe_assert(struct kretprobe_instance *ri, Index: linux-2.6.25-rc3/kernel/kprobes.c =================================================================== --- linux-2.6.25-rc3.orig/kernel/kprobes.c +++ linux-2.6.25-rc3/kernel/kprobes.c @@ -72,6 +72,17 @@ DEFINE_MUTEX(kprobe_mutex); /* Protects DEFINE_SPINLOCK(kretprobe_lock); /* Protects kretprobe_inst_table */ static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL; +/* + * Normally, functions that we'd want to prohibit kprobes in, are marked + * __kprobes. But, there are cases where such functions already belong to + * a different section (__sched for preempt_schedule) + * + * For such cases, we now have a blacklist + */ +struct kprobe_blackpoint kprobe_blacklist[] = { + {"preempt_schedule",}, + {NULL} /* Terminator */ + #ifdef __ARCH_WANT_KPROBES_INSN_SLOT /* * kprobe->ainsn.insn points to the copy of the instruction to be @@ -492,9 +503,22 @@ static int __kprobes register_aggr_kprob static int __kprobes in_kprobes_functions(unsigned long addr) { + struct kprobe_blackpoint *kb; + if (addr >= (unsigned long)__kprobes_text_start && addr < (unsigned long)__kprobes_text_end) return -EINVAL; + /* + * If there exists a kprobe_blacklist, verify and + * fail any probe registration in the prohibited area + */ + for (kb = kprobe_blacklist; kb->name != NULL; kb++) { + if (kb->start_addr) { + if (addr >= kb->start_addr && + addr < (kb->start_addr + kb->range)) + return -EINVAL; + } + } return 0; } @@ -805,6 +829,11 @@ void __kprobes unregister_kretprobe(stru static int __init init_kprobes(void) { int i, err = 0; + unsigned long offset = 0, size = 0; + char *modname, namebuf[128]; + const char *symbol_name; + void *addr; + struct kprobe_blackpoint *kb; /* FIXME allocate the probe table, currently defined statically */ /* initialize all list heads */ @@ -813,6 +842,28 @@ static int __init init_kprobes(void) INIT_HLIST_HEAD(&kretprobe_inst_table[i]); } + /* + * Lookup and populate the kprobe_blacklist. + * + * Unlike the kretprobe blacklist, we'll need to determine + * the range of addresses that belong to the said functions, + * since a kprobe need not necessarily be at the beginning + * of a function. + */ + for (kb = kprobe_blacklist; kb->name != NULL; kb++) { + kprobe_lookup_name(kb->name, addr); + if (!addr) + continue; + + kb->start_addr = (unsigned long)addr; + symbol_name = kallsyms_lookup(kb->start_addr, + &size, &offset, &modname, namebuf); + if (!symbol_name) + kb->range = 0; + else + kb->range = size; + } + if (kretprobe_blacklist_size) { /* lookup the function address from its name */ for (i = 0; kretprobe_blacklist[i].name != NULL; i++) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/