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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: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Namhyung 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: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Masami Hiramatsu 2016-05-29 00:15:13 +09:00 committed by Arnaldo Carvalho de Melo
parent dcd1e2a7ba
commit 11870d714a
1 changed files with 22 additions and 10 deletions
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32
tools/perf/util/symbol.c
View File

@ -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))
goto proc_kallsyms;
}
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)))