| Message ID | ZSRaDcJNARUUWUwS@work (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ima: Add __counted_by for struct modsig and use struct_size() | expand |
On Mon, Oct 09, 2023 at 01:52:45PM -0600, Gustavo A. R. Silva wrote: > 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 <gustavoars@kernel.org> Looks right; good catch on moving the assignment. Reviewed-by: Kees Cook <keescook@chromium.org>
On Mon, 2023-10-09 at 13:52 -0600, Gustavo A. R. Silva wrote: > 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 <gustavoars@kernel.org> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
On Mon, 09 Oct 2023 13:52:45 -0600, Gustavo A. R. Silva wrote: > 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. > > [...] Applied to for-next/hardening, thanks! [1/1] ima: Add __counted_by for struct modsig and use struct_size() https://git.kernel.org/kees/c/68a8f644575b Take care,
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;
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 <gustavoars@kernel.org> --- security/integrity/ima/ima_modsig.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)