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Re: [Qemu-block] [PATCH v4 05/21] nbd/server: Hoist length check to qmp_

From: Vladimir Sementsov-Ogievskiy
Subject: Re: [Qemu-block] [PATCH v4 05/21] nbd/server: Hoist length check to qmp_nbd_server_add
Date: Fri, 18 Jan 2019 09:48:06 +0000

17.01.2019 22:36, Eric Blake wrote:
> We only had two callers to nbd_export_new; qemu-nbd.c always
> passed a valid offset/length pair (because it already checked
> the file length, to ensure that offset was in bounds), while
> blockdev-nbd.c always passed 0/-1.  Then nbd_export_new reduces
> the size to a multiple of BDRV_SECTOR_SIZE (can only happen
> when offset is not sector-aligned, since bdrv_getlength()
> currently rounds up), which can result in offset being greater
> than the enforced length, but that's not fatal (the server
> rejects client requests that exceed the advertised length).
> However, I'm finding it easier to work with the code if we are
> consistent on having both callers pass in a valid length, and
> just assert that things are sane in nbd_export_new, meaning
> that no negative values were passed, and that offset+size does
> not exceed 63 bits (as that really is a fundamental limit to
> later operations, whether we use off_t or uint64_t).
> Signed-off-by: Eric Blake <address@hidden>

Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>

Best regards,

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