Commits
Rabin Vincent committed bd975d1eead
cifs: fix crash due to race in hmac(md5) handling
The secmech hmac(md5) structures are present in the TCP_Server_Info
struct and can be shared among multiple CIFS sessions. However, the
server mutex is not currently held when these structures are allocated
and used, which can lead to a kernel crashes, as in the scenario below:
mount.cifs(8) #1 mount.cifs(8) #2
Is secmech.sdeschmaccmd5 allocated?
// false
Is secmech.sdeschmaccmd5 allocated?
// false
secmech.hmacmd = crypto_alloc_shash..
secmech.sdeschmaccmd5 = kzalloc..
sdeschmaccmd5->shash.tfm = &secmec.hmacmd;
secmech.sdeschmaccmd5 = kzalloc
// sdeschmaccmd5->shash.tfm
// not yet assigned
crypto_shash_update()
deref NULL sdeschmaccmd5->shash.tfm
Unable to handle kernel paging request at virtual address 00000030
epc : 8027ba34 crypto_shash_update+0x38/0x158
ra : 8020f2e8 setup_ntlmv2_rsp+0x4bc/0xa84
Call Trace:
crypto_shash_update+0x38/0x158
setup_ntlmv2_rsp+0x4bc/0xa84
build_ntlmssp_auth_blob+0xbc/0x34c
sess_auth_rawntlmssp_authenticate+0xac/0x248
CIFS_SessSetup+0xf0/0x178
cifs_setup_session+0x4c/0x84
cifs_get_smb_ses+0x2c8/0x314
cifs_mount+0x38c/0x76c
cifs_do_mount+0x98/0x440
mount_fs+0x20/0xc0
vfs_kern_mount+0x58/0x138
do_mount+0x1e8/0xccc
SyS_mount+0x88/0xd4
syscall_common+0x30/0x54
Fix this by locking the srv_mutex around the code which uses these
hmac(md5) structures. All the other secmech algos already have similar
locking.
Fixes: 95dc8dd14e2e84cc ("Limit allocation of crypto mechanisms to dialect which requires")
Signed-off-by: Rabin Vincent <rabinv@axis.com>
Acked-by: Sachin Prabhu <sprabhu@redhat.com>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>