Bug 1193874

Created attachment 993086 [details]
File: backtrace

Created attachment 993087 [details]
File: cgroup

Created attachment 993088 [details]
File: core_backtrace

Created attachment 993089 [details]
File: dso_list

Created attachment 993090 [details]
File: environ

Created attachment 993091 [details]
File: exploitable

Created attachment 993092 [details]
File: limits

Created attachment 993093 [details]
File: maps

Created attachment 993094 [details]
File: open_fds

Created attachment 993095 [details]
File: proc_pid_status

The cause of the bug is a missing NULL check:

mnt_dir_expanded = realpath(m->mnt_dir, NULL);

realpath() may return NULL, as it does on my system when the process has no permission to iterate the mnt_dir path.

I get a segmentation fault with the unpatched code, but adding a NULL check as suggested above seems to fix the problem.  I just added the line marked below in file src/encfs_wrapper.cpp from source RPM cryptkeeper-0.9.5-10.fc21.src.rpm

        for (;;) {
                char *mnt_dir_expanded;
                struct mntent *m = getmntent(f);
                if (!m) break;
                mnt_dir_expanded = realpath(m->mnt_dir, NULL);
+                if (mnt_dir_expanded == NULL) continue;  // added by mjf
                if (strcmp(mount_dir_expanded, mnt_dir_expanded)==0) {
                        free(mnt_dir_expanded);
                        return true;
                }
        }

This just causes that iteration of the loop to be skipped when realpath() returns NULL (which seems to be when m->mnt_dir is also NULL).  I don't know if this is always the right thing to do, but it seems to work on my fedora 21 system.

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Reproduced somehow similar behaviour in Fedora 23, 64 bits. Not exact backtrace as showed in "Description of the problem", but stack trace shows some coincidences:
* segfault in 
    libc-2.22.so[7f506346f000+1b7000]
* Stack trace of thread 10592:
    #0  0x00007f506350d93e __strcmp_sse2_unaligned (libc.so.6)

I would like this problem to be fixed, but I'm not sure if trying to reopen this bug is the correct way to do it.
Would you please, tell me if I should give more information here, or rather open a new bug report?
Best Regards.

The bug is still present in Fedora 23.  I'm still using the patched version that I described in comment #12 above.  My only problem with it is that the icon no longer shows in the task bar under KDE.  But it still works if I click in the blank space where the icon ought to be.