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[ Upstream commit d0259a856afca31d699b706ed5e2adf11086c73b ] In p9_client_write() and p9_client_read_once(), if the server incorrectly replies with success but a negative write/read count then we would consider written (negative) <= rsize (positive) because both variables were signed. Make variables unsigned to avoid this problem. The reproducer linked below now fails with the following error instead of a null pointer deref: 9pnet: bogus RWRITE count (4294967295 > 3) Reported-by: Robert Morris <rtm@mit.edu> Closes: https://lore.kernel.org/16271.1734448631@26-5-164.dynamic.csail.mit.edu Message-ID: <20250319-9p_unsigned_rw-v3-1-71327f1503d0@codewreck.org> Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com> Signed-off-by: Dominique Martinet <asmadeus@codewreck.org> Signed-off-by: Sasha Levin <sashal@kernel.org>