3.16.60-rc1 review patch. If anyone has any objections, please let me know.
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From: Kenny Yu kennyyu@fb.com
commit 6496bb72bf20c1c7e4d6be44dfa663163e709116 upstream.
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.com
Signed-off-by: Kenny Yu kennyyu@fb.com Reviewed-by: Omar Sandoval osandov@fb.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Ben Hutchings ben@decadent.org.uk --- kernel/trace/trace_uprobe.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -430,7 +430,8 @@ static int create_trace_uprobe(int argc, 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;