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Commit 11870d71 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Arnaldo Carvalho de Melo
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perf symbols: Introduce filename__readable to check readability 



Introduce filename__readable to check readability by opening the file
directly. Since the access(R_OK) just checks the readability based on
real UID/GID, it is ignored that the effective UID/GID and capabilities
for some special file (e.g.  /proc/kcore).

filename__readable() directly opens given file with O_RDONLY so that the
kernel checks it by effective UID/GID and capabilities.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Acked-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20160528151513.16098.97576.stgit@devbox


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent dcd1e2a7

tools/perf/util/symbol.c

+22 −10
Original line number Diff line number Diff line
@@ -1641,6 +1641,20 @@ static int find_matching_kcore(struct map *map, char *dir, size_t dir_sz) 
	return ret;

}



/*

 * Use open(O_RDONLY) to check readability directly instead of access(R_OK)

 * since access(R_OK) only checks with real UID/GID but open() use effective

 * UID/GID and actual capabilities (e.g. /proc/kcore requires CAP_SYS_RAWIO).

 */

static bool filename__readable(const char *file)

{

	int fd = open(file, O_RDONLY);

	if (fd < 0)

		return false;

	close(fd);

	return true;

}



static char *dso__find_kallsyms(struct dso *dso, struct map *map)

{

	u8 host_build_id[BUILD_ID_SIZE];
@@ -1668,7 +1682,6 @@ static char *dso__find_kallsyms(struct dso *dso, struct map *map) 
	/* Use /proc/kallsyms if possible */

	if (is_host) {

		DIR *d;

		int fd;



		/* If no cached kcore go with /proc/kallsyms */

		d = opendir(path);
@@ -1677,16 +1690,15 @@ static char *dso__find_kallsyms(struct dso *dso, struct map *map) 
		closedir(d);



		/*

		 * Do not check the build-id cache, until we know we cannot use

		 * /proc/kcore.

		 * Do not check the build-id cache, unless we know we cannot use

		 * /proc/kcore or module maps don't match to /proc/kallsyms.

		 * To check readability of /proc/kcore, do not use access(R_OK)

		 * since /proc/kcore requires CAP_SYS_RAWIO to read and access

		 * can't check it.

		 */

		fd = open("/proc/kcore", O_RDONLY);

		if (fd != -1) {

			close(fd);

			/* If module maps match go with /proc/kallsyms */

			if (!validate_kcore_addresses("/proc/kallsyms", map))

		if (filename__readable("/proc/kcore") &&

		    !validate_kcore_addresses("/proc/kallsyms", map))

			goto proc_kallsyms;

		}



		/* Find kallsyms in build-id cache with kcore */

		if (!find_matching_kcore(map, path, sizeof(path)))