Messages in this thread | | | Date | Fri, 20 Mar 2015 13:18:07 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf: fix race in build_id_cache__add_s() |
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On Fri, Mar 20, 2015 at 11:37:25AM +0100, Milos Vyletel wrote: > int build_id_cache__add_s(const char *sbuild_id, const char *debugdir, > const char *name, bool is_kallsyms, bool is_vdso) > { > ... > if (access(filename, F_OK)) { > ^--------------------------------------------------------- [1] > if (is_kallsyms) { > if (copyfile("/proc/kallsyms", filename)) > goto out_free; > } else if (link(realname, filename) && copyfile(name, filename)) > ^-----------------------------^------------- [2] > \------------ [3] > goto out_free; > } > ... > > when multiple instances of perf record get to [1] at more or less same time and > run access() one or more may get failure because the file does not exist yet > (since the first instance did not have chance to link it yet). at this point the > race moves to link() at [2] where first thread to get there links file and goes > on but second one gets -EEXIST so it runs copyfile [3] which truncates the file.
nice.. :-\
Acked-by: Jiri Olsa <jolsa@kernel.org>
in addition we should use some inter-perf lock on all .debug dir operations
jirka
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