From: Matt Cowell <matt.cow...@nokia.com>
Some symlinks in /proc, such as those under /proc/[pid]/fd,
/proc/[pid]/cwd, and /proc/[pid]/exe that are not real and should not
have readlink called on them. These look like symlinks, but behave like
hardlinks. Readlink does not return actual paths. Previously
pseudo_fix_path would expand files such as /dev/stdin to paths such as
/proc/6680/fd/pipe:[1270830076] which do not exist.
This issue affects:
- deleted files
- deleted directories
- fifos
- sockets
- anon_inodes (epoll, eventfd, inotify, signalfd, timerfd, etc)
Testing:
- run_tests: all tests passed. Checked the test output to make
sure the new codepath gets executed.
- perftest: measured time before and after applying the patch
had insignificant differences (roughly ~1%)
- world build: completed without warning/errors
Signed-off-by: Sakib Sajal <sakib.sa...@windriver.com>
---
pseudo_util.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/pseudo_util.c b/pseudo_util.c
index b6980c2..b35a34e 100644
--- a/pseudo_util.c
+++ b/pseudo_util.c
@@ -21,6 +21,8 @@
#include <sys/time.h>
#include <unistd.h>
#include <limits.h>
+#include <sys/vfs.h>
+#include <linux/magic.h>
/* see the comments below about (*real_regcomp)() */
#include <dlfcn.h>
@@ -29,6 +31,11 @@
#include "pseudo_ipc.h"
#include "pseudo_db.h"
+/* O_PATH is defined in glibc 2.16 and later only */
+#ifndef O_PATH
+#define O_PATH 010000000
+#endif
+
struct pseudo_variables {
char *key;
size_t key_len;
@@ -678,6 +685,26 @@ pseudo_append_element(char *newpath, char *root, size_t
allocated, char **pcurre
*/
if (!leave_this && is_dir) {
int is_link = S_ISLNK(buf->st_mode);
+
+ /* do not expand symlinks in the proc filesystem, since they
may not be real */
+ if (is_link) {
+ struct statfs sfs;
+ int fd;
+
+ /* statfs follows symlinks, so use fstatfs */
+ fd = open(newpath, O_CLOEXEC | O_PATH | O_NOFOLLOW);
+ if (-1 != fd) {
+ if (0 == fstatfs(fd, &sfs) && sfs.f_type ==
PROC_SUPER_MAGIC) {
+ pseudo_debug(PDBGF_PATH | PDBGF_VERBOSE,
+ "pae: '%s' is procfs symlink,
not expanding\n",
+ newpath);
+ is_link = 0;
+ }
+
+ close(fd);
+ }
+ }
+
if (link_recursion >= PSEUDO_MAX_LINK_RECURSION && is_link) {
pseudo_diag("link recursion too deep, not expanding
path '%s'.\n", newpath);
is_link = 0;
--
2.25.1
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