Commit 6496bb72 authored by Kenny Yu's avatar Kenny Yu Committed by Steven Rostedt (VMware)

uprobe: Find last occurrence of ':' when parsing uprobe PATH:OFFSET

Previously, `create_trace_uprobe` found the *first* occurence
of the ':' character when parsing `PATH:OFFSET` for a uprobe.
However, if the path contains a ':' character, then the function
would parse the path incorrectly. Even worse, if the path does not
exist, the subsequent call to `kern_path()` would set `ret` to
`ENOENT`, leading to very cryptic errno values in user space.

The fix is to find the *last* occurence of ':'.

How to repro:: The write fails with "No such file or directory", suggesting
incorrectly that the `uprobe_events` file does not exist.

  $ mkdir testing && cd testing
  $ cp /bin/bash .
  $ cp /bin/bash ./bash:with:colon
  $ echo "p:uprobes/p__root_testing_bash_0x6 /root/testing/bash:0x6" > /sys/kernel/debug/tracing/uprobe_events     # this works
  $ echo "p:uprobes/p__root_testing_bash_with_colon_0x6 /root/testing/bash:with:colon:0x6" >> /sys/kernel/debug/tracing/uprobe_events     # this doesn't
  -bash: echo: write error: No such file or directory

With the patch:

  $ echo "p:uprobes/p__root_testing_bash_0x6 /root/testing/bash:0x6" > /sys/kernel/debug/tracing/uprobe_events     # this still works
  $ echo "p:uprobes/p__root_testing_bash_with_colon_0x6 /root/testing/bash:with:colon:0x6" >> /sys/kernel/debug/tracing/uprobe_events     # this works now too!
  $ cat /sys/kernel/debug/tracing/uprobe_events
  p:uprobes/p__root_testing_bash_0x6 /root/testing/bash:0x0000000000000006
  p:uprobes/p__root_testing_bash_with_colon_0x6 /root/testing/bash:with:colon:0x0000000000000006

Link: http://lkml.kernel.org/r/20170113165834.4081016-1-kennyyu@fb.comSigned-off-by: default avatarKenny Yu <kennyyu@fb.com>
Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 0c744ea4
......@@ -431,7 +431,8 @@ static int create_trace_uprobe(int argc, char **argv)
pr_info("Probe point is not specified.\n");
return -EINVAL;
}
arg = strchr(argv[1], ':');
/* Find the last occurrence, in case the path contains ':' too. */
arg = strrchr(argv[1], ':');
if (!arg) {
ret = -EINVAL;
goto fail_address_parse;
......
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