On Sat, Jun 11, 2011 at 4:41 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > On Fri, 10 Jun 2011 05:49:46 -0700 > Connor Hansen <cmdkhh@xxxxxxxxx> wrote: > >> On Fri, Jun 10, 2011 at 5:14 AM, Suresh Jayaraman <sjayaraman@xxxxxxx> wrote: >> > On 06/10/2011 05:33 PM, Connor Hansen wrote: >> >> On Fri, Jun 10, 2011 at 4:37 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: >> >>> On Fri, 10 Jun 2011 02:57:21 +0200 (CEST) >> >>> Uffing <mp3project@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: >> >>> >> >>>> >> >>>> <snip> >> >>>>> call in get_dfs_path() >> >>>>> rc = CIFSTCon(xid, pSesInfo, temp_unc, NULL, nls_codepage); >> >>>>> >> >>>>> function header for CIFSTCon >> >>>>> int CIFSTCon(unsigned int xid, struct cifs_ses *ses, >> >>>>> const char *tree, struct cifs_tcon *tcon, >> >>>>> const struct nls_table *nls_codepage) >> >>>>> >> >>>>> get_dfs_path() is passing struct cifs_tcon *tcon as NULL >> >>>>> >> >>>>> from config: CONFIG_CIFS_WEAK_PW_HASH=y >> >>>>> >> >>>>> in CIFSTCon >> >>>>> >> >>>>> #ifdef CONFIG_CIFS_WEAK_PW_HASH >> >>>>> 3222 if ((global_secflags & CIFSSEC_MAY_LANMAN) && >> >>>>> 3223 (ses->server->secType == LANMAN)) >> >>>>> 3224 calc_lanman_hash(tcon->password, >> >>>>> ses->server->cryptkey, >> >>>>> >> >>>>> in calc_lanman_hash tcon is dereferenced(tcon->password) without being >> >>>>> checked if null >> >>>>> >> >>>>> 3225 ses->server->sec_mode & >> >>>>> 3226 SECMODE_PW_ENCRYPT ? >> >>>>> true : false, >> >>>>> 3227 bcc_ptr); >> >>>>> 3228 else >> >>>>> 3229 #endif /* CIFS_WEAK_PW_HASH */ >> >>>>> >> >>>>> Connor >> >>>> >> >>>> >> >>>> Ave all >> >>>> >> >>>> I recompiled kernel 3.0-rc1 (hadn't enabled CONFIG_DEBUG_INFO=y) and put >> >>>> the oops (with the new adresses) through gdb per instruction of Jeff. And >> >>>> Connor was spot on! >> >>>> >> >>>> <qoute oops> >> >>>> BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0 >> >>>> IP: [<ffffffffa041e286>] CIFSTCon+0xf6/0x4d0 [cifs] >> >>>> </qoute oops> >> >>>> >> >>>> <qoute gdb> >> >>>> This GDB was configured as "x86_64-linux-gnu". >> >>>> For bug reporting instructions, please see: >> >>>> <http://www.gnu.org/software/gdb/bugs/>... >> >>>> Reading symbols from >> >>>> /lib/modules/3.0.0-rc1-debug/kernel/fs/cifs/cifs.ko...done. >> >>>> (gdb) list *(CIFSTCon+0xf6) >> >>>> 0xc2b6 is in CIFSTCon (fs/cifs/connect.c:3230). >> >>>> 3225 ses->server->sec_mode & >> >>>> 3226 SECMODE_PW_ENCRYPT ? >> >>>> true : false, >> >>>> 3227 bcc_ptr); >> >>>> 3228 else >> >>>> 3229 #endif /* CIFS_WEAK_PW_HASH */ >> >>>> 3230 rc = SMBNTencrypt(tcon->password, >> >>>> ses->server->cryptkey, >> >>>> 3231 bcc_ptr); >> >>>> 3232 >> >>>> 3233 bcc_ptr += CIFS_AUTH_RESP_SIZE; >> >>>> 3234 if (ses->capabilities & CAP_UNICODE) { >> >>>> (gdb) >> >>>> </qoute gdb> >> >>>> >> >>> >> >>> (cc'ing Sean F. since I suspect this regression is due to his changes) >> >>> >> >>> Thanks for the analysis, Martijn and Connor... >> >>> >> >>> What sort of server are you mounting here? It looks like it's using >> >>> share-level security, so it's either very old or is a samba server >> >>> configured that way. >> >>> >> >>> I suspect that commit c1508ca236 is the culprit. With that, we call >> >>> into expand_dfs_referral on every mount attempt. Previously we only >> >>> called into there when we got back an EREMOTE error and that would >> >>> have been unlikely on a share-level security connection. >> >>> >> >>> I think there are several possible solutions, but since Sean was in >> >>> here most recently I'd like to have his opinion. >> >> >> >> I don't know enough about cifs but this call in fs/cifs/connect.c >> >> >> >> 2268: rc = CIFSTCon(xid, pSesInfo, temp_unc, NULL, nls_codepage); >> >> >> >> will always result in a null pointer derefence as CIFSTCon uses the >> >> cifs_tcon struct for passwords without verification >> > >> > Yes, I too was hovering around this code path today and it doesn't look >> > correct. Specifically, the call from cifs_dfs_path to CIFSTCon with >> > cifs_tcon as NULL seems wrong. I tried to do dig history a bit with `git >> > blame`, but couldn't figure out the commit that introduced this. >> > >> > >> > -- >> > Suresh Jayaraman >> > >> >> git annotate fs/cifs/connect.c >> 1da177e4 (Linus Torvalds 2005-04-16 15:20:36 -0700 2268) >> rc = CIFSTCon(xid, pSesInfo, temp_unc, NULL, nls_codepage); >> >> this was valid at the time to simply get the rc, and the code was checked >> if ((rc == 0) && (tcon != NULL)) { // first use of tcon in >> CIFSTCon back then..... >> >> >> after a loooooong look, i found the patch which changed it >> >> 00e485b0 >> commit 00e485b0198ea4f509341373f1d9adb0a5977a2f >> Author: Jeff Layton <jlayton@xxxxxxxxxx> >> Date: Fri Dec 5 20:41:21 2008 -0500 >> >> cifs: store password in tcon >> >> cifs: store password in tcon >> >> Each tcon has its own password for share-level security. Store it in >> the tcon and wipe it clean and free it when freeing the tcon. When >> doing the tree connect with share-level security, use the tcon password >> instead of the session password. >> >> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> >> Signed-off-by: Steve French <sfrench@xxxxxxxxxx> >> > > Yep, mea culpa. This patch should fix it. Martin, can you test it? > Anyone else have comments? > > Thanks... Looks good to me, Connor > > -----------------------[snip]-------------------- > > [PATCH] cifs: correctly handle NULL tcon pointer in CIFSTCon > > Long ago (in commit 00e485b0), I added some code to handle share-level > passwords in CIFSTCon. That code ignored the fact that it's legit to > pass in a NULL tcon pointer when connecting to the IPC$ share on the > server. > > This wasn't really a problem until recently as we only called CIFSTCon > this way when the server returned -EREMOTE. With the introduction of > commit c1508ca2 however, it gets called this way on every mount, causing > an oops when share-level security is in effect. > > Fix this by simply treating a NULL tcon pointer as if user-level > security were in effect. I'm not aware of any servers that protect the > IPC$ share with a specific password anyway. Also, add a comment to the > top of CIFSTCon to ensure that we don't make the same mistake again. > > Reported-by: Martijn Uffing <mp3project@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > --- > fs/cifs/connect.c | 6 +++++- > 1 files changed, 5 insertions(+), 1 deletions(-) > > diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c > index 7b6cad2..fa5a5d7 100644 > --- a/fs/cifs/connect.c > +++ b/fs/cifs/connect.c > @@ -3174,6 +3174,10 @@ out: > return rc; > } > > +/* > + * Issue a TREE_CONNECT request. Note that for IPC$ shares, that the tcon > + * pointer may be NULL. > + */ > int > CIFSTCon(unsigned int xid, struct cifs_ses *ses, > const char *tree, struct cifs_tcon *tcon, > @@ -3208,7 +3212,7 @@ CIFSTCon(unsigned int xid, struct cifs_ses *ses, > pSMB->AndXCommand = 0xFF; > pSMB->Flags = cpu_to_le16(TCON_EXTENDED_SECINFO); > bcc_ptr = &pSMB->Password[0]; > - if ((ses->server->sec_mode) & SECMODE_USER) { > + if (!tcon || (ses->server->sec_mode & SECMODE_USER)) { > pSMB->PasswordLength = cpu_to_le16(1); /* minimum */ > *bcc_ptr = 0; /* password is null byte */ > bcc_ptr++; /* skip password */ > -- > 1.7.5.2 > > -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
