Messages in this thread Patch in this message | | | Date | Sun, 30 Sep 2012 21:42:24 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 6/7] uprobes: Fix uprobe_copy_insn() race with itself |
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install_breakpoint() is called under mm->mmap_sem, this protects set_swbp() but not uprobe_copy_insn(). Two or more different tasks can call install_breakpoint()->uprobe_copy_insn() at the same time, this leads to numerous problems if UPROBE_COPY_INSN is not set.
Just for example, the second copy_insn() can corrupt the already analyzed/fixuped uprobe->arch.insn and race with handle_swbp().
This patch simply adds uprobe->copy_mutex to serialize this code. We could probably reuse ->consumer_rwsem, but this would mean that consumer->handler() can not use mm->mmap_sem, not good.
Note: this is another temporary ugly hack until we move this logic into uprobe_register().
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/events/uprobes.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 5c0c1b0..8410388 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -89,6 +89,7 @@ struct uprobe { struct rb_node rb_node; /* node in the rb tree */ atomic_t ref; struct rw_semaphore consumer_rwsem; + struct mutex copy_mutex; /* TODO: kill me and UPROBE_COPY_INSN */ struct list_head pending_list; struct uprobe_consumer *consumers; struct inode *inode; /* Also hold a ref to inode */ @@ -444,6 +445,7 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset) uprobe->inode = igrab(inode); uprobe->offset = offset; init_rwsem(&uprobe->consumer_rwsem); + mutex_init(&uprobe->copy_mutex); /* add to uprobes_tree, sorted on inode:offset */ cur_uprobe = insert_uprobe(uprobe); @@ -578,6 +580,10 @@ static int uprobe_copy_insn(struct uprobe *uprobe, struct file *file, if (uprobe->flags & UPROBE_COPY_INSN) return ret; + mutex_lock(&uprobe->copy_mutex); + if (uprobe->flags & UPROBE_COPY_INSN) + goto out; + ret = copy_insn(uprobe, file); if (ret) goto out; @@ -598,6 +604,8 @@ static int uprobe_copy_insn(struct uprobe *uprobe, struct file *file, uprobe->flags |= UPROBE_COPY_INSN; ret = 0; out: + mutex_unlock(&uprobe->copy_mutex); + return ret; } -- 1.5.5.1
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