Hi,
I came across an interesting issue recently.
Suppose you have a filesystem which supports case-insensitive file names
(like VFAT, but in this particular case 'NSS' - Novell Storage Services).
And support you export some subdirectory (or sub-volume) using a
non-canonical name.
i.e. you "mkdir /path/export", the put "/path/EXPORT" in /etc/exports and
mount server:/path/EXPORT from some client.
This all works until the export cache times out and the kernel asks mountd
if "/path/export" is exported. mountd says "no" and suddenly all accesses
fail.
I don't think much of case-insensitive file names, but I suspect we should
either make this work, it issue a warning as to why it is failing.
A simple work around is to export the canonical name and use it when
mounting. But if the sysadmin doesn't know they need to, they are unlikely
to guess.
I don't think there is any API to test if a name is canonical, or to get the
canonical name, so I cannot see any way in advance to see if this problem
situation has arisen. So the only option I can think of is to fix it.
The following patch (or something much like it for an older nfs-utils) seems
to do the trick.
What do people think? Is this a reasonable thing to do? Is it likely to
have negative consequences that I haven't thought of?
Thanks,
NeilBrown
diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c
index 9a1bb2767ac2..2d91db76b867 100644
--- a/utils/mountd/cache.c
+++ b/utils/mountd/cache.c
@@ -377,6 +377,28 @@ static char *next_mnt(void **v, char *p)
return me->mnt_dir;
}
+static int same_path(char *child, char *parent, int len)
+{
+ static char p[PATH_MAX];
+ struct stat sc, sp;
+ if (len <= 0)
+ len = strlen(child);
+ strncpy(p, child, len);
+ p[len] = 0;
+ if (strcmp(p, parent) == 0)
+ return 1;
+
+ if (lstat(p, &sc) != 0)
+ return 0;
+ if (lstat(parent, &sp) != 0)
+ return 0;
+ if (sc.st_dev != sp.st_dev)
+ return 0;
+ if (sc.st_ino != sp.st_ino)
+ return 0;
+ return 1;
+}
+
static int is_subdirectory(char *child, char *parent)
{
/* Check is child is strictly a subdirectory of
@@ -387,7 +409,7 @@ static int is_subdirectory(char *child, char *parent)
if (strcmp(parent, "/") == 0 && child[1] != 0)
return 1;
- return (strncmp(child, parent, l) == 0 && child[l] == '/');
+ return (same_path(child, parent, l) && child[l] == '/');
}
static int path_matches(nfs_export *exp, char *path)
@@ -396,7 +418,7 @@ static int path_matches(nfs_export *exp, char *path)
* exact match, or does the export have CROSSMOUNT, and path
* is a descendant?
*/
- return strcmp(path, exp->m_export.e_path) == 0
+ return same_path(path, exp->m_export.e_path, 0)
|| ((exp->m_export.e_flags & NFSEXP_CROSSMOUNT)
&& is_subdirectory(path, exp->m_export.e_path));
}
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