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| author | Oleg Nesterov <oleg@redhat.com> | 2012-09-30 20:31:41 +0200 |
|---|---|---|
| committer | Oleg Nesterov <oleg@redhat.com> | 2012-10-07 21:19:43 +0200 |
| commit | 4710f05fd146d4739e57a8832a3abc5bd3bf0997 (patch) | |
| tree | 459f64b5243d621c85b34abf90e3892cca69e502 | |
| parent | cb9a19fe4aa51afa34786bd383e6614fa0083d58 (diff) | |
| download | talos-obmc-linux-4710f05fd146d4739e57a8832a3abc5bd3bf0997.tar.gz talos-obmc-linux-4710f05fd146d4739e57a8832a3abc5bd3bf0997.zip | |
uprobes: Fix prepare_uprobe() race with itself
install_breakpoint() is called under mm->mmap_sem, this protects
set_swbp() but not prepare_uprobe(). Two or more different tasks
can call install_breakpoint()->prepare_uprobe() 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>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| -rw-r--r-- | 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 4f315fa94c52..7f62b30c4172 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 prepare_uprobe(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 prepare_uprobe(struct uprobe *uprobe, struct file *file, uprobe->flags |= UPROBE_COPY_INSN; out: + mutex_unlock(&uprobe->copy_mutex); + return ret; } |
