From: Harald Freudenberger Date: Mon, 3 Aug 2026 08:33:36 +0000 (+0200) Subject: s390/zcrypt: Improve EP11 CPRB length and overflow checks X-Git-Tag: v7.2-rc7~2^2~2 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=17ac0bc866fc624cd05f022dcd8b730c0af11bb1;p=thirdparty%2Flinux.git s390/zcrypt: Improve EP11 CPRB length and overflow checks The xcrb_msg_to_type6_ep11cprb_msgx() function lacks proper input validation, creating security vulnerabilities: 1. Missing minimum size validation: The ep11_cprb structure and subsequent payload fields (pld_tag, pld_lenfmt) are copied from userspace without verifying sufficient buffer length. 2. Arithmetic overflow in length calculations: CEIL4 alignment could overflow, bypassing size checks and enabling buffer overflows. 3. The payload is asn1 encoded but the function just uses a simple c struct overlay to access some fields of the payload. Fix by using size_t for length calculations, adding U32_MAX boundary checks after alignment, and validating minimum request size and minimum reply size before copying from userspace. Do a very simple asn1 parsing of the payload up to the function value field. Fixes: e2c6d91eb8b1 ("s390/zcrypt: Rework domain processing within zcrypt device driver") Signed-off-by: Harald Freudenberger Cc: stable@vger.kernel.org # 7.1+ Reviewed-by: Holger Dengler Signed-off-by: Vasily Gorbik --- diff --git a/drivers/s390/crypto/zcrypt_msgtype6.c b/drivers/s390/crypto/zcrypt_msgtype6.c index 3e19e79d747c..7e1f76c935ee 100644 --- a/drivers/s390/crypto/zcrypt_msgtype6.c +++ b/drivers/s390/crypto/zcrypt_msgtype6.c @@ -19,6 +19,7 @@ #include #include #include +#include #include "ap_bus.h" #include "zcrypt_api.h" @@ -34,6 +35,9 @@ #define CEXXC_RESPONSE_TYPE_XCRB 1 #define CEXXC_RESPONSE_TYPE_EP11 2 +/* smallest possible EP11 payload size */ +#define MIN_EP11_PAYLOAD_SIZE 5 + MODULE_AUTHOR("IBM Corporation"); MODULE_DESCRIPTION("Cryptographic Coprocessor (message type 6), " \ "Copyright IBM Corp. 2001, 2023"); @@ -438,12 +442,59 @@ static int xcrb_msg_to_type6cprb_msgx(bool userspace, struct ap_message *ap_msg, return 0; } +/* + * Simple asn1 int reader/decoder helper function + * Returns number of bytes processed or < 0 on failure + * Only accepts int length values of 1, 2 or 4. + */ +static inline int asn1_int_decode(const u8 *buf, size_t intlen, u32 *u) +{ + switch (intlen) { + case 1: + *u = (u32)(*buf); + return 1; + case 2: + *u = (u32)get_unaligned_be16(buf); + return 2; + case 4: + *u = (u32)get_unaligned_be32(buf); + return 4; + default: + return -EINVAL; + } +} + +/* + * Simple asn1 length parse helper function + * Returns number of bytes processed or < 0 on failure + * Only accepts length encoded within the length octet + * or for long form 1, 2 or 4 octet length bytes. + */ +static inline int asn1_length_decode(const u8 *buf, size_t buflen, u32 *u) +{ + int i; + + if (buflen < 1) + return -EINVAL; + + if (*buf < 128) { + *u = (u32)(*buf & 0x7F); + return 1; + } + + i = *buf & 0x7F; + if (--buflen < i) + return -EINVAL; + i = asn1_int_decode(++buf, i, u); + + return i < 0 ? i : i + 1; +} + static int xcrb_msg_to_type6_ep11cprb_msgx(bool userspace, struct ap_message *ap_msg, struct ep11_urb *xcrb, unsigned int *fcode, unsigned int *domain) { - unsigned int lfmt; static struct type6_hdr static_type6_ep11_hdr = { .type = 0x06, .rqid = {0x00, 0x01}, @@ -455,34 +506,32 @@ static int xcrb_msg_to_type6_ep11cprb_msgx(bool userspace, struct ap_message *ap struct { struct type6_hdr hdr; union { - struct { - struct ep11_cprb cprbx; - unsigned char pld_tag; /* fixed value 0x30 */ - unsigned char pld_lenfmt; /* length format */ - } __packed; + struct ep11_cprb cprbx; DECLARE_FLEX_ARRAY(u8, userdata); }; } __packed * msg = ap_msg->msg; - struct pld_hdr { - unsigned char func_tag; /* fixed value 0x4 */ - unsigned char func_len; /* fixed value 0x4 */ - unsigned int func_val; /* function ID */ - unsigned char dom_tag; /* fixed value 0x4 */ - unsigned char dom_len; /* fixed value 0x4 */ - unsigned int dom_val; /* domain id */ - } __packed * payload_hdr = NULL; - - if (CEIL4(xcrb->req_len) < xcrb->req_len) - return -EINVAL; /* overflow after alignment*/ + size_t req_len, rep_len, pld_len; + unsigned char *pld; + int offs = 0, i; + unsigned int u; - /* length checks */ - ap_msg->len = sizeof(struct type6_hdr) + CEIL4(xcrb->req_len); + /* request length and overflow checks */ + if (xcrb->req_len < sizeof(struct ep11_cprb) + MIN_EP11_PAYLOAD_SIZE) + return -EINVAL; + req_len = CEIL4(xcrb->req_len); + if (req_len < xcrb->req_len || req_len > U32_MAX) + return -EINVAL; + ap_msg->len = sizeof(struct type6_hdr) + req_len; if (ap_msg->len > ap_msg->bufsize) return -EINVAL; - if (CEIL4(xcrb->resp_len) < xcrb->resp_len) - return -EINVAL; /* overflow after alignment*/ + /* reply length and overflow checks */ + if (xcrb->resp_len < sizeof(struct ep11_cprb)) + return -EINVAL; + rep_len = CEIL4(xcrb->resp_len); + if (rep_len < xcrb->resp_len || rep_len > U32_MAX) + return -EINVAL; /* prepare type6 header */ msg->hdr = static_type6_ep11_hdr; @@ -491,26 +540,51 @@ static int xcrb_msg_to_type6_ep11cprb_msgx(bool userspace, struct ap_message *ap /* Import CPRB data from the ioctl input parameter */ if (z_copy_from_user(userspace, msg->userdata, - (char __force __user *)xcrb->req, xcrb->req_len)) { + (char __force __user *)xcrb->req, xcrb->req_len)) return -EFAULT; - } - if ((msg->pld_lenfmt & 0x80) == 0x80) { /*ext.len.fmt 2 or 3*/ - switch (msg->pld_lenfmt & 0x03) { - case 1: - lfmt = 2; - break; - case 2: - lfmt = 3; - break; - default: - return -EINVAL; - } - } else { - lfmt = 1; /* length format #1 */ - } - payload_hdr = (struct pld_hdr *)((&msg->pld_lenfmt) + lfmt); - *fcode = payload_hdr->func_val & 0xFFFF; + pld = msg->userdata + sizeof(struct ep11_cprb); + pld_len = msg->cprbx.payload_len; + if (pld_len != xcrb->req_len - sizeof(struct ep11_cprb)) + return -EINVAL; + /* + * At this point pld_len is always >= MIN_EP11_PAYLOAD_SIZE + * and the smallest supported asn1 payload is: + * payload tag (1 octet) + * payload length (1-5 octets) + * function tag (1 octet) + * function length (1-5 octets) + * function value (1-4 octets) + */ + + /* payload tag */ + if (pld[offs++] != 0x30) + return -EINVAL; + /* payload length field */ + i = asn1_length_decode(pld + offs, pld_len - offs, &u); + if (i < 0) + return -EINVAL; + offs += i; + if (offs >= pld_len || u > pld_len - offs) + return -EINVAL; + /* function tag */ + if (pld[offs++] != 0x04) + return -EINVAL; + /* function length */ + if (offs >= pld_len) + return -EINVAL; + i = asn1_length_decode(pld + offs, pld_len - offs, &u); + if (i < 0) + return -EINVAL; + offs += i; + if (offs >= pld_len || u > pld_len - offs) + return -EINVAL; + /* function value */ + i = asn1_int_decode(pld + offs, u, &u); + if (i < 0) + return -EINVAL; + offs += i; + *fcode = 0xFFFF & u; /* enable special processing based on the cprbs flags special bit */ if (msg->cprbx.flags & 0x20)