From 71434f2fcba5c22d6e0d51878ba8e241a5dea5fb Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sun, 30 Sep 2012 21:12:44 +0200 Subject: [PATCH] uprobes: Fix the racy uprobe->flags manipulation Multiple threads can manipulate uprobe->flags, this is obviously unsafe. For example mmap can set UPROBE_COPY_INSN while register tries to set UPROBE_RUN_HANDLER, the latter can also race with can_skip_sstep() which clears UPROBE_SKIP_SSTEP. Change this code to use bitops. Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju --- kernel/events/uprobes.c | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 7f62b30c4172..c92651d619ca 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -79,11 +79,11 @@ static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ]; static atomic_t uprobe_events = ATOMIC_INIT(0); /* Have a copy of original instruction */ -#define UPROBE_COPY_INSN 0x1 +#define UPROBE_COPY_INSN 0 /* Dont run handlers when first register/ last unregister in progress*/ -#define UPROBE_RUN_HANDLER 0x2 +#define UPROBE_RUN_HANDLER 1 /* Can skip singlestep */ -#define UPROBE_SKIP_SSTEP 0x4 +#define UPROBE_SKIP_SSTEP 2 struct uprobe { struct rb_node rb_node; /* node in the rb tree */ @@ -94,7 +94,7 @@ struct uprobe { struct uprobe_consumer *consumers; struct inode *inode; /* Also hold a ref to inode */ loff_t offset; - int flags; + unsigned long flags; struct arch_uprobe arch; }; @@ -423,7 +423,7 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe) spin_unlock(&uprobes_treelock); /* For now assume that the instruction need not be single-stepped */ - uprobe->flags |= UPROBE_SKIP_SSTEP; + __set_bit(UPROBE_SKIP_SSTEP, &uprobe->flags); return u; } @@ -466,7 +466,7 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) { struct uprobe_consumer *uc; - if (!(uprobe->flags & UPROBE_RUN_HANDLER)) + if (!test_bit(UPROBE_RUN_HANDLER, &uprobe->flags)) return; down_read(&uprobe->consumer_rwsem); @@ -577,11 +577,11 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file, { int ret = 0; - if (uprobe->flags & UPROBE_COPY_INSN) + if (test_bit(UPROBE_COPY_INSN, &uprobe->flags)) return ret; mutex_lock(&uprobe->copy_mutex); - if (uprobe->flags & UPROBE_COPY_INSN) + if (test_bit(UPROBE_COPY_INSN, &uprobe->flags)) goto out; ret = copy_insn(uprobe, file); @@ -601,7 +601,7 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file, UPROBE_SWBP_INSN_SIZE > PAGE_SIZE); smp_wmb(); /* pairs with rmb() in find_active_uprobe() */ - uprobe->flags |= UPROBE_COPY_INSN; + set_bit(UPROBE_COPY_INSN, &uprobe->flags); out: mutex_unlock(&uprobe->copy_mutex); @@ -852,7 +852,7 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer * uprobe->consumers = NULL; __uprobe_unregister(uprobe); } else { - uprobe->flags |= UPROBE_RUN_HANDLER; + set_bit(UPROBE_RUN_HANDLER, &uprobe->flags); } } @@ -885,7 +885,7 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume if (consumer_del(uprobe, uc)) { if (!uprobe->consumers) { __uprobe_unregister(uprobe); - uprobe->flags &= ~UPROBE_RUN_HANDLER; + clear_bit(UPROBE_RUN_HANDLER, &uprobe->flags); } } @@ -1346,10 +1346,10 @@ bool uprobe_deny_signal(void) */ static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs) { - if (uprobe->flags & UPROBE_SKIP_SSTEP) { + if (test_bit(UPROBE_SKIP_SSTEP, &uprobe->flags)) { if (arch_uprobe_skip_sstep(&uprobe->arch, regs)) return true; - uprobe->flags &= ~UPROBE_SKIP_SSTEP; + clear_bit(UPROBE_SKIP_SSTEP, &uprobe->flags); } return false; } @@ -1473,7 +1473,7 @@ static void handle_swbp(struct pt_regs *regs) * new and not-yet-analyzed uprobe at the same address, restart. */ smp_rmb(); /* pairs with wmb() in install_breakpoint() */ - if (unlikely(!(uprobe->flags & UPROBE_COPY_INSN))) + if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags))) goto restart; utask = current->utask; -- 2.20.1