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| H A D | nfs42.h | diff 26e177cffce2880b7e85578ef1947fef4e01f9e7 Thu Jan 25 08:51:28 CST 2024 Jorge Mora <jmora1300@gmail.com> NFSv4.2: fix listxattr maximum XDR buffer size
[ Upstream commit bcac8bff90a6ee1629f90669cdb9d28fb86049b0 ]
Switch order of operations to avoid creating a short XDR buffer:
e.g., buflen = 12, old xdrlen = 12, new xdrlen = 20.
Having a short XDR buffer leads to lxa_maxcount be a few bytes
less than what is needed to retrieve the whole list when using
a buflen as returned by a call with size = 0:
buflen = listxattr(path, NULL, 0);
buf = malloc(buflen);
buflen = listxattr(path, buf, buflen);
For a file with one attribute (name = '123456'), the first call
with size = 0 will return buflen = 12 ('user.123456\x00').
The second call with size = 12, sends LISTXATTRS with
lxa_maxcount = 12 + 8 (cookie) + 4 (array count) = 24. The
XDR buffer needs 8 (cookie) + 4 (array count) + 4 (name count)
+ 6 (name len) + 2 (padding) + 4 (eof) = 28 which is 4 bytes
shorter than the lxa_maxcount provided in the call.
Fixes: 04a5da690e8f ("NFSv4.2: define limits and sizes for user xattr handling")
Signed-off-by: Jorge Mora <mora@netapp.com>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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