From 03cdfaad491e82e4a66593c6e149ddae0421df59 Mon Sep 17 00:00:00 2001 From: Nicolai Stange Date: Thu, 26 May 2016 23:19:51 +0200 Subject: [PATCH] lib/mpi: mpi_read_from_buffer(): return error code mpi_read_from_buffer() reads a MPI from a buffer into a newly allocated MPI instance. It expects the buffer's leading two bytes to contain the number of bits, followed by the actual payload. On failure, it returns NULL and updates the in/out argument ret_nread somewhat inconsistently: - If the given buffer is too short to contain the leading two bytes encoding the number of bits or their value is unsupported, then ret_nread will be cleared. - If the allocation of the resulting MPI instance fails, ret_nread is left as is. The only user of mpi_read_from_buffer(), digsig_verify_rsa(), simply checks for a return value of NULL and returns -ENOMEM if that happens. While this is all of cosmetic nature only, there is another error condition which currently isn't detectable by the caller of mpi_read_from_buffer(): if the given buffer is too small to hold the number of bits as encoded in its first two bytes, the return value will be non-NULL and *ret_nread > 0. In preparation of communicating this condition to the caller, let mpi_read_from_buffer() return error values by means of the ERR_PTR() mechanism. Make the sole caller of mpi_read_from_buffer(), digsig_verify_rsa(), check the return value for IS_ERR() rather than == NULL. If IS_ERR() is true, return the associated error value rather than the fixed -ENOMEM. Signed-off-by: Nicolai Stange Signed-off-by: Herbert Xu --- lib/digsig.c | 12 ++++++++---- lib/mpi/mpicoder.c | 6 +++--- 2 files changed, 11 insertions(+), 7 deletions(-) diff --git a/lib/digsig.c b/lib/digsig.c index 07be6c1ef4e2..a121cbc5a46b 100644 --- a/lib/digsig.c +++ b/lib/digsig.c @@ -104,16 +104,18 @@ static int digsig_verify_rsa(struct key *key, datap = pkh->mpi; endp = ukp->data + ukp->datalen; - err = -ENOMEM; - for (i = 0; i < pkh->nmpi; i++) { unsigned int remaining = endp - datap; pkey[i] = mpi_read_from_buffer(datap, &remaining); - if (!pkey[i]) + if (IS_ERR(pkey[i])) { + err = PTR_ERR(pkey[i]); goto err; + } datap += remaining; } + err = -ENOMEM; + mblen = mpi_get_nbits(pkey[0]); mlen = DIV_ROUND_UP(mblen, 8); @@ -126,8 +128,10 @@ static int digsig_verify_rsa(struct key *key, nret = siglen; in = mpi_read_from_buffer(sig, &nret); - if (!in) + if (IS_ERR(in)) { + err = PTR_ERR(in); goto err; + } res = mpi_alloc(mpi_get_nlimbs(in) * 2); if (!res) diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c index eda34aba017e..350abaf4bee7 100644 --- a/lib/mpi/mpicoder.c +++ b/lib/mpi/mpicoder.c @@ -86,12 +86,12 @@ MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread) MPI val = NULL; if (*ret_nread < 2) - goto leave; + return ERR_PTR(-EINVAL); nbits = buffer[0] << 8 | buffer[1]; if (nbits > MAX_EXTERN_MPI_BITS) { pr_info("MPI: mpi too large (%u bits)\n", nbits); - goto leave; + return ERR_PTR(-EINVAL); } buffer += 2; nread = 2; @@ -100,7 +100,7 @@ MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread) nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); val = mpi_alloc(nlimbs); if (!val) - return NULL; + return ERR_PTR(-ENOMEM); i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; i %= BYTES_PER_MPI_LIMB; val->nbits = nbits; -- 2.20.1