Messages in this thread Patch in this message | | | Date | Thu, 5 Jun 2014 07:38:57 -0700 | From | tip-bot for Oleg Nesterov <> | Subject | [tip:perf/core] uprobes: Shift ->readpage check from __copy_insn( ) to uprobe_register() |
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Commit-ID: 41ccba029e9492dd0fc1bf5c23b72c6322a6dfe9 Gitweb: http://git.kernel.org/tip/41ccba029e9492dd0fc1bf5c23b72c6322a6dfe9 Author: Oleg Nesterov <oleg@redhat.com> AuthorDate: Mon, 19 May 2014 20:40:54 +0200 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Thu, 5 Jun 2014 12:30:07 +0200
uprobes: Shift ->readpage check from __copy_insn() to uprobe_register()
copy_insn() fails with -EIO if ->readpage == NULL, but this error is not propagated unless uprobe_register() path finds ->mm which already mmaps this file. In this case (say) "perf record" does not actually install the probe, but the user can't know about this.
Move this check into uprobe_register() so that this problem can be detected earlier and reported to user.
Note: this is still not perfect,
- copy_insn() and arch_uprobe_analyze_insn() should be called by uprobe_register() but this is not simple, we need vm_file for read_mapping_page() (although perhaps we can pass NULL), and we need ->mm for is_64bit_mm() (although this logic is broken anyway).
- uprobe_register() should be called by create_trace_uprobe(), not by probe_event_enable(), so that an error can be detected at "perf probe -x" time. This also needs more changes in the core uprobe code, uprobe register/unregister interface was poorly designed from the very beginning.
Reported-by: Denys Vlasenko <dvlasenk@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Hugh Dickins <hughd@google.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20140519184054.GA6750@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> --- kernel/events/uprobes.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 3b02c72..c56b13e 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -536,9 +536,6 @@ static int __copy_insn(struct address_space *mapping, struct file *filp, void *insn, int nbytes, loff_t offset) { struct page *page; - - if (!mapping->a_ops->readpage) - return -EIO; /* * Ensure that the page that has the original instruction is * populated and in page-cache. @@ -879,6 +876,9 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer * if (!uc->handler && !uc->ret_handler) return -EINVAL; + /* copy_insn()->read_mapping_page() needs ->readpage() */ + if (!inode->i_mapping->a_ops->readpage) + return -EIO; /* Racy, just to catch the obvious mistakes */ if (offset > i_size_read(inode)) return -EINVAL;
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