Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions).
Also, relocate `hdr->raw_pkcs7_len = sig_len;` so that the __counted_by annotation has effect, and flex-array member `raw_pkcs7` can be properly bounds-checked at run-time. While there, use struct_size() helper, instead of the open-coded version, to calculate the size for the allocation of the whole flexible structure, including of course, the flexible-array member. This code was found with the help of Coccinelle, and audited and fixed manually. Signed-off-by: Gustavo A. R. Silva <[email protected]> --- security/integrity/ima/ima_modsig.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c index 3e7bee30080f..3265d744d5ce 100644 --- a/security/integrity/ima/ima_modsig.c +++ b/security/integrity/ima/ima_modsig.c @@ -29,7 +29,7 @@ struct modsig { * storing the signature. */ int raw_pkcs7_len; - u8 raw_pkcs7[]; + u8 raw_pkcs7[] __counted_by(raw_pkcs7_len); }; /* @@ -65,10 +65,11 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len, buf_len -= sig_len + sizeof(*sig); /* Allocate sig_len additional bytes to hold the raw PKCS#7 data. */ - hdr = kzalloc(sizeof(*hdr) + sig_len, GFP_KERNEL); + hdr = kzalloc(struct_size(hdr, raw_pkcs7, sig_len), GFP_KERNEL); if (!hdr) return -ENOMEM; + hdr->raw_pkcs7_len = sig_len; hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len); if (IS_ERR(hdr->pkcs7_msg)) { rc = PTR_ERR(hdr->pkcs7_msg); @@ -77,7 +78,6 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len, } memcpy(hdr->raw_pkcs7, buf + buf_len, sig_len); - hdr->raw_pkcs7_len = sig_len; /* We don't know the hash algorithm yet. */ hdr->hash_algo = HASH_ALGO__LAST; -- 2.34.1
