On Sun Jan 21, 2024 at 7:50 PM EET, Lukas Wunner wrote: > Jonathan suggests adding cleanup.h support for x509_certificate structs: > https://lore.kernel.org/all/20231003153937.000034ca@xxxxxxxxxx/ You have suggested-by. Use link/closes/whatever tag if you want to link that message (and rip off this paragraph). Since the whole feature is new maybe it would make sense to remind about __cleanup__ attribute and its use or at least link: https://lwn.net/Articles/934679/. You are writing it like "every knows this already". > Introduce a DEFINE_FREE() macro and use it in x509_cert_parse() and > x509_key_preparse(). These are the only functions where scope-based DEFINE_FREE() macro already exists. This patch just invokes the already existing macro. > x509_certificate allocation currently makes sense. Another user will > be introduced with the upcoming SPDM library (Security Protocol and > Data Model) for PCI device authentication. What is it and why we care about it here? > > Unlike most other DEFINE_FREE() macros, this one not only has to check So they are not DEFINE_FREE() macros but locations that invoke DEFINE_FREE() (i.e. DEFINE_FREE9() invocations). > for NULL, but also for ERR_PTR() before calling x509_free_certificate() > at end of scope. That's because the "constructor" of x509_certificate > structs, x509_cert_parse(), may return an ERR_PTR(). "Unlike usual DEFINE_FREE() invocations, return value may also contain error, matching the possible return values of x509_cert_parse()." > I've compared the Assembler output before/after and while I couldn't > spot a functional difference, I did notice an annoying superfluous check > being added to each function: The tail of the commit message looks more like diary, notes, plans than anything senseful for a commit message. > x509_free_certificate() at end of scope. It knows whether "cert" is > an ERR_PTR() because of the explicit "if (IS_ERR(cert))" check at the > top of the function, but it doesn't know whether it's NULL. In fact > it can *never* be NULL because x509_cert_parse() only returns either > a valid pointer or an ERR_PTR(). > > I've tried adding __attribute__((returns_nonnull)) to x509_cert_parse() > but the compiler ignores it due to commit a3ca86aea507 > ("Add '-fno-delete-null-pointer-checks' to gcc CFLAGS"). > > * x509_cert_parse() now checks that "cert" is not an ERR_PTR() before > calling x509_free_certificate() at end of scope. The compiler doesn't > know that kzalloc() never returns an ERR_PTR(). > > I've tried telling the compiler that by amending kmalloc() with > "if (IS_ERR(ptr)) __builtin_unreachable();", but the result was > disappointing: While it succeeded in eliminating the superfluous > ERR_PTR() check, total vmlinux size increased by 448 bytes. > > I could add such a clause locally to x509_cert_parse() instead of > kmalloc(), but it would require additions to compiler-*.h. > (clang uses a different syntax for these annotations.) > > Despite the annoying extra checks, I think the gain in readability > justifies the conversion. > > Suggested-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> > --- Maybe you want to put tail here. > crypto/asymmetric_keys/x509_cert_parser.c | 42 +++++++++++-------------------- > crypto/asymmetric_keys/x509_parser.h | 3 +++ > crypto/asymmetric_keys/x509_public_key.c | 31 +++++++---------------- > 3 files changed, 27 insertions(+), 49 deletions(-) > > diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c > index 487204d..e597ac6 100644 > --- a/crypto/asymmetric_keys/x509_cert_parser.c > +++ b/crypto/asymmetric_keys/x509_cert_parser.c > @@ -60,24 +60,23 @@ void x509_free_certificate(struct x509_certificate *cert) > */ > struct x509_certificate *x509_cert_parse(const void *data, size_t datalen) > { > - struct x509_certificate *cert; > - struct x509_parse_context *ctx; > + struct x509_certificate *cert __free(x509_free_certificate); > + struct x509_parse_context *ctx __free(kfree) = NULL; > struct asymmetric_key_id *kid; > long ret; > > - ret = -ENOMEM; > cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL); > if (!cert) > - goto error_no_cert; > + return ERR_PTR(-ENOMEM); > cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL); > if (!cert->pub) > - goto error_no_ctx; > + return ERR_PTR(-ENOMEM); > cert->sig = kzalloc(sizeof(struct public_key_signature), GFP_KERNEL); > if (!cert->sig) > - goto error_no_ctx; > + return ERR_PTR(-ENOMEM); > ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL); > if (!ctx) > - goto error_no_ctx; > + return ERR_PTR(-ENOMEM); > > ctx->cert = cert; > ctx->data = (unsigned long)data; > @@ -85,7 +84,7 @@ struct x509_certificate *x509_cert_parse(const void *data, size_t datalen) > /* Attempt to decode the certificate */ > ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen); > if (ret < 0) > - goto error_decode; > + return ERR_PTR(ret); > > /* Decode the AuthorityKeyIdentifier */ > if (ctx->raw_akid) { > @@ -95,20 +94,19 @@ struct x509_certificate *x509_cert_parse(const void *data, size_t datalen) > ctx->raw_akid, ctx->raw_akid_size); > if (ret < 0) { > pr_warn("Couldn't decode AuthKeyIdentifier\n"); > - goto error_decode; > + return ERR_PTR(ret); > } > } > > - ret = -ENOMEM; > cert->pub->key = kmemdup(ctx->key, ctx->key_size, GFP_KERNEL); > if (!cert->pub->key) > - goto error_decode; > + return ERR_PTR(-ENOMEM); > > cert->pub->keylen = ctx->key_size; > > cert->pub->params = kmemdup(ctx->params, ctx->params_size, GFP_KERNEL); > if (!cert->pub->params) > - goto error_decode; > + return ERR_PTR(-ENOMEM); > > cert->pub->paramlen = ctx->params_size; > cert->pub->algo = ctx->key_algo; > @@ -116,33 +114,23 @@ struct x509_certificate *x509_cert_parse(const void *data, size_t datalen) > /* Grab the signature bits */ > ret = x509_get_sig_params(cert); > if (ret < 0) > - goto error_decode; > + return ERR_PTR(ret); > > /* Generate cert issuer + serial number key ID */ > kid = asymmetric_key_generate_id(cert->raw_serial, > cert->raw_serial_size, > cert->raw_issuer, > cert->raw_issuer_size); > - if (IS_ERR(kid)) { > - ret = PTR_ERR(kid); > - goto error_decode; > - } > + if (IS_ERR(kid)) > + return ERR_CAST(kid); > cert->id = kid; > > /* Detect self-signed certificates */ > ret = x509_check_for_self_signed(cert); > if (ret < 0) > - goto error_decode; > - > - kfree(ctx); > - return cert; > + return ERR_PTR(ret); > > -error_decode: > - kfree(ctx); > -error_no_ctx: > - x509_free_certificate(cert); > -error_no_cert: > - return ERR_PTR(ret); > + return_ptr(cert); > } > EXPORT_SYMBOL_GPL(x509_cert_parse); > > diff --git a/crypto/asymmetric_keys/x509_parser.h b/crypto/asymmetric_keys/x509_parser.h > index 97a886c..d2dfe50 100644 > --- a/crypto/asymmetric_keys/x509_parser.h > +++ b/crypto/asymmetric_keys/x509_parser.h > @@ -5,6 +5,7 @@ > * Written by David Howells (dhowells@xxxxxxxxxx) > */ > > +#include <linux/cleanup.h> > #include <linux/time.h> > #include <crypto/public_key.h> > #include <keys/asymmetric-type.h> > @@ -44,6 +45,8 @@ struct x509_certificate { > * x509_cert_parser.c > */ > extern void x509_free_certificate(struct x509_certificate *cert); > +DEFINE_FREE(x509_free_certificate, struct x509_certificate *, > + if (!IS_ERR_OR_NULL(_T)) x509_free_certificate(_T)) > extern struct x509_certificate *x509_cert_parse(const void *data, size_t datalen); > extern int x509_decode_time(time64_t *_t, size_t hdrlen, > unsigned char tag, > diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c > index 6a4f00b..00ac715 100644 > --- a/crypto/asymmetric_keys/x509_public_key.c > +++ b/crypto/asymmetric_keys/x509_public_key.c > @@ -161,12 +161,11 @@ int x509_check_for_self_signed(struct x509_certificate *cert) > */ > static int x509_key_preparse(struct key_preparsed_payload *prep) > { > - struct asymmetric_key_ids *kids; > - struct x509_certificate *cert; > + struct x509_certificate *cert __free(x509_free_certificate); > + struct asymmetric_key_ids *kids __free(kfree) = NULL; > + char *p, *desc __free(kfree) = NULL; > const char *q; > size_t srlen, sulen; > - char *desc = NULL, *p; > - int ret; > > cert = x509_cert_parse(prep->data, prep->datalen); > if (IS_ERR(cert)) > @@ -188,9 +187,8 @@ static int x509_key_preparse(struct key_preparsed_payload *prep) > } > > /* Don't permit addition of blacklisted keys */ > - ret = -EKEYREJECTED; > if (cert->blacklisted) > - goto error_free_cert; > + return -EKEYREJECTED; > > /* Propose a description */ > sulen = strlen(cert->subject); > @@ -202,10 +200,9 @@ static int x509_key_preparse(struct key_preparsed_payload *prep) > q = cert->raw_serial; > } > > - ret = -ENOMEM; > desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL); > if (!desc) > - goto error_free_cert; > + return -ENOMEM; > p = memcpy(desc, cert->subject, sulen); > p += sulen; > *p++ = ':'; > @@ -215,16 +212,14 @@ static int x509_key_preparse(struct key_preparsed_payload *prep) > > kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL); > if (!kids) > - goto error_free_desc; > + return -ENOMEM; > kids->id[0] = cert->id; > kids->id[1] = cert->skid; > kids->id[2] = asymmetric_key_generate_id(cert->raw_subject, > cert->raw_subject_size, > "", 0); > - if (IS_ERR(kids->id[2])) { > - ret = PTR_ERR(kids->id[2]); > - goto error_free_kids; > - } > + if (IS_ERR(kids->id[2])) > + return PTR_ERR(kids->id[2]); > > /* We're pinning the module by being linked against it */ > __module_get(public_key_subtype.owner); > @@ -242,15 +237,7 @@ static int x509_key_preparse(struct key_preparsed_payload *prep) > cert->sig = NULL; > desc = NULL; > kids = NULL; > - ret = 0; > - > -error_free_kids: > - kfree(kids); > -error_free_desc: > - kfree(desc); > -error_free_cert: > - x509_free_certificate(cert); > - return ret; > + return 0; > } > > static struct asymmetric_key_parser x509_key_parser = { BR, Jarkko
