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NFSD: Fix exposure in nfsd4_decode_bitmap()

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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: d1c263a031 ("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>
This commit is contained in:
Chuck Lever 2021-11-14 15:16:04 -05:00 committed by J. Bruce Fields
parent 80479eb862
commit c0019b7db1
1 changed files with 2 additions and 5 deletions
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7
fs/nfsd/nfs4xdr.c
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@ -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;
}