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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: VXA4NF3LNZ5UD664JICNP55EGO4DTLFJ X-Message-ID-Hash: VXA4NF3LNZ5UD664JICNP55EGO4DTLFJ X-MailFrom: lvivier@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 3/20/24 05:27, David Gibson wrote: > On Tue, Mar 19, 2024 at 11:13:40AM +0100, Laurent Vivier wrote: >> In write_remainder() 'skip' is the offset to start the operation from >> in the iovec array. >> >> In iov_skip_bytes(), 'skip' is also the offset in the iovec array but >> 'offset' is the first unskipped byte in the iovec entry. >> >> As write_remainder() uses 'skip' for both, 'skip' is reset to the >> first unskipped byte in the iovec entry rather to staying the first >> unskipped byte in the iovec array. >> >> Fix the problem by introducing a new variable not to overwrite 'skip' >> on each loop. >> >> Fixes: 8bdb0883b441 ("util: Add write_remainder() helper") >> Cc: david@gibson.dropbear.id.au >> Signed-off-by: Laurent Vivier > > Ouch. *dons paper bag* > > I believe this is correct as it stands, but.. > >> --- >> util.c | 7 ++++--- >> 1 file changed, 4 insertions(+), 3 deletions(-) >> >> diff --git a/util.c b/util.c >> index 3b2393d6bfa8..eee53aed811b 100644 >> --- a/util.c >> +++ b/util.c >> @@ -533,13 +533,14 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags, >> int write_remainder(int fd, const struct iovec *iov, int iovcnt, size_t skip) >> { >> int i; >> + size_t offset; >> >> - while ((i = iov_skip_bytes(iov, iovcnt, skip, &skip)) < iovcnt) { >> + while ((i = iov_skip_bytes(iov, iovcnt, skip, &offset)) < iovcnt) { >> ssize_t rc; >> >> if (skip) { > > .. it would be more optimal if you checked for offset != 0 rather than > skip != 0 here. Otherwise even once we've written an entire buffer, > we'll continue to write the rest of the buffers one by one, rather > than writing them all with a writev(). > Yes, you're right. I missed that. Thanks, Laurent