This implements the worst-case compression size querying interface for
lz4hc, based on the logic originally used by pstore.

Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 crypto/lz4hc.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/crypto/lz4hc.c b/crypto/lz4hc.c
index 2be14f054daf..cf6f38a1c35b 100644
--- a/crypto/lz4hc.c
+++ b/crypto/lz4hc.c
@@ -118,6 +118,24 @@ static int lz4hc_decompress_crypto(struct crypto_tfm *tfm, 
const u8 *src,
        return __lz4hc_decompress_crypto(src, slen, dst, dlen, NULL);
 }
 
+static int __lz4hc_zbufsize_crypto(unsigned int slen, unsigned int *dlen)
+{
+       *dlen = LZ4_compressBound(slen);
+       return 0;
+}
+
+static int lz4hc_szbufsize(struct crypto_scomp *tfm, unsigned int slen,
+                          unsigned int *dlen, void *ctx)
+{
+       return __lz4hc_zbufsize_crypto(slen, dlen);
+}
+
+static int lz4hc_zbufsize_crypto(struct crypto_tfm *tfm, unsigned int slen,
+                                unsigned int *dlen)
+{
+       return __lz4hc_zbufsize_crypto(slen, dlen);
+}
+
 static struct crypto_alg alg_lz4hc = {
        .cra_name               = "lz4hc",
        .cra_flags              = CRYPTO_ALG_TYPE_COMPRESS,
@@ -128,7 +146,8 @@ static struct crypto_alg alg_lz4hc = {
        .cra_exit               = lz4hc_exit,
        .cra_u                  = { .compress = {
        .coa_compress           = lz4hc_compress_crypto,
-       .coa_decompress         = lz4hc_decompress_crypto } }
+       .coa_decompress         = lz4hc_decompress_crypto,
+       .coa_zbufsize           = lz4hc_zbufsize_crypto } }
 };
 
 static struct scomp_alg scomp = {
@@ -136,6 +155,7 @@ static struct scomp_alg scomp = {
        .free_ctx               = lz4hc_free_ctx,
        .compress               = lz4hc_scompress,
        .decompress             = lz4hc_sdecompress,
+       .zbufsize               = lz4hc_szbufsize,
        .base                   = {
                .cra_name       = "lz4hc",
                .cra_driver_name = "lz4hc-scomp",
-- 
2.17.1

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