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Subject[PATCH 4.18 040/197] sunrpc: Dont use stack buffer with scatterlist
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Laura Abbott <labbott@redhat.com>

[ Upstream commit 44090cc876926277329e1608bafc01b9f6da627f ]

Fedora got a bug report from NFS:

kernel BUG at include/linux/scatterlist.h:143!
...
RIP: 0010:sg_init_one+0x7d/0x90
..
make_checksum+0x4e7/0x760 [rpcsec_gss_krb5]
gss_get_mic_kerberos+0x26e/0x310 [rpcsec_gss_krb5]
gss_marshal+0x126/0x1a0 [auth_rpcgss]
? __local_bh_enable_ip+0x80/0xe0
? call_transmit_status+0x1d0/0x1d0 [sunrpc]
call_transmit+0x137/0x230 [sunrpc]
__rpc_execute+0x9b/0x490 [sunrpc]
rpc_run_task+0x119/0x150 [sunrpc]
nfs4_run_exchange_id+0x1bd/0x250 [nfsv4]
_nfs4_proc_exchange_id+0x2d/0x490 [nfsv4]
nfs41_discover_server_trunking+0x1c/0xa0 [nfsv4]
nfs4_discover_server_trunking+0x80/0x270 [nfsv4]
nfs4_init_client+0x16e/0x240 [nfsv4]
? nfs_get_client+0x4c9/0x5d0 [nfs]
? _raw_spin_unlock+0x24/0x30
? nfs_get_client+0x4c9/0x5d0 [nfs]
nfs4_set_client+0xb2/0x100 [nfsv4]
nfs4_create_server+0xff/0x290 [nfsv4]
nfs4_remote_mount+0x28/0x50 [nfsv4]
mount_fs+0x3b/0x16a
vfs_kern_mount.part.35+0x54/0x160
nfs_do_root_mount+0x7f/0xc0 [nfsv4]
nfs4_try_mount+0x43/0x70 [nfsv4]
? get_nfs_version+0x21/0x80 [nfs]
nfs_fs_mount+0x789/0xbf0 [nfs]
? pcpu_alloc+0x6ca/0x7e0
? nfs_clone_super+0x70/0x70 [nfs]
? nfs_parse_mount_options+0xb40/0xb40 [nfs]
mount_fs+0x3b/0x16a
vfs_kern_mount.part.35+0x54/0x160
do_mount+0x1fd/0xd50
ksys_mount+0xba/0xd0
__x64_sys_mount+0x21/0x30
do_syscall_64+0x60/0x1f0
entry_SYSCALL_64_after_hwframe+0x49/0xbe

This is BUG_ON(!virt_addr_valid(buf)) triggered by using a stack
allocated buffer with a scatterlist. Convert the buffer for
rc4salt to be dynamically allocated instead.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1615258
Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sunrpc/auth_gss/gss_krb5_crypto.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

--- a/net/sunrpc/auth_gss/gss_krb5_crypto.c
+++ b/net/sunrpc/auth_gss/gss_krb5_crypto.c
@@ -169,7 +169,7 @@ make_checksum_hmac_md5(struct krb5_ctx *
struct scatterlist sg[1];
int err = -1;
u8 *checksumdata;
- u8 rc4salt[4];
+ u8 *rc4salt;
struct crypto_ahash *md5;
struct crypto_ahash *hmac_md5;
struct ahash_request *req;
@@ -183,14 +183,18 @@ make_checksum_hmac_md5(struct krb5_ctx *
return GSS_S_FAILURE;
}

+ rc4salt = kmalloc_array(4, sizeof(*rc4salt), GFP_NOFS);
+ if (!rc4salt)
+ return GSS_S_FAILURE;
+
if (arcfour_hmac_md5_usage_to_salt(usage, rc4salt)) {
dprintk("%s: invalid usage value %u\n", __func__, usage);
- return GSS_S_FAILURE;
+ goto out_free_rc4salt;
}

checksumdata = kmalloc(GSS_KRB5_MAX_CKSUM_LEN, GFP_NOFS);
if (!checksumdata)
- return GSS_S_FAILURE;
+ goto out_free_rc4salt;

md5 = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(md5))
@@ -258,6 +262,8 @@ out_free_md5:
crypto_free_ahash(md5);
out_free_cksum:
kfree(checksumdata);
+out_free_rc4salt:
+ kfree(rc4salt);
return err ? GSS_S_FAILURE : 0;
}


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