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    Subject[PATCH 5.15 122/279] NFSD: Fix exposure in nfsd4_decode_bitmap()
    Date
    From: Chuck Lever <chuck.lever@oracle.com>

    [ Upstream commit c0019b7db1d7ac62c711cda6b357a659d46428fe ]

    rtm@csail.mit.edu reports:
    > nfsd4_decode_bitmap4() will write beyond bmval[bmlen-1] if the RPC
    > directs it to do so. This can cause nfsd4_decode_state_protect4_a()
    > to write client-supplied data beyond the end of
    > nfsd4_exchange_id.spo_must_allow[] when called by
    > nfsd4_decode_exchange_id().

    Rewrite the loops so nfsd4_decode_bitmap() cannot iterate beyond
    @bmlen.

    Reported by: rtm@csail.mit.edu
    Fixes: d1c263a031e8 ("NFSD: Replace READ* macros in nfsd4_decode_fattr()")
    Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/nfsd/nfs4xdr.c | 7 ++-----
    1 file changed, 2 insertions(+), 5 deletions(-)

    diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
    index cf030ebe28275..266d5152c3216 100644
    --- a/fs/nfsd/nfs4xdr.c
    +++ b/fs/nfsd/nfs4xdr.c
    @@ -288,11 +288,8 @@ nfsd4_decode_bitmap4(struct nfsd4_compoundargs *argp, u32 *bmval, u32 bmlen)
    p = xdr_inline_decode(argp->xdr, count << 2);
    if (!p)
    return nfserr_bad_xdr;
    - i = 0;
    - while (i < count)
    - bmval[i++] = be32_to_cpup(p++);
    - while (i < bmlen)
    - bmval[i++] = 0;
    + for (i = 0; i < bmlen; i++)
    + bmval[i] = (i < count) ? be32_to_cpup(p++) : 0;

    return nfs_ok;
    }
    --
    2.33.0


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