Resolve writable shadow_fd destination in sendfile#65
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ChuWeiChang wants to merge 1 commit intosysprog21:mainfrom
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Resolve writable shadow_fd destination in sendfile#65ChuWeiChang wants to merge 1 commit intosysprog21:mainfrom
ChuWeiChang wants to merge 1 commit intosysprog21:mainfrom
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jserv
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| /* Guest test: verify sendfile with a shadow-memfd input FD. | ||
| * sendfile must resolve the host fd through that shadow path via | ||
| * find_by_host_fd(); this test confirms data integrity end-to-end. |
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Does this test case reflect the problem you are addressing? If so, prove it.
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Yes, the test reflects the problem, though the original comments did not reflect the output FD as the relevant one. I've updated them.
When intercepting sendfile with out_fd as shadow_fd, forward_sendfile mistakenly treat it as host_fd instead of shadow_sp. Fix this by explicitly querying the out_fd's FD table entry. If shadow_writeback is enabled, extract and write to shadow_sp instead. Change-Id: Ifbe431c557f8d10cb2f4ab221176da336e35e067
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Fixes #64 and also help with test gap 5 in #38
Overview
There is a routing bug in
forward_sendfileinseccomp_dispatch.cwhere destination shadow FDs were bypassing the virtual kernel (shadow_sp) and writing directly to the underlying physical host_fd.What this PR does
fd_table_entrylookup for the destinationout_fdprior to the emulation loop.test/guest/sendfile-test.cSummary by cubic
Fixes sendfile routing when
out_fdis a writeback shadow. Writes now go toshadow_sp(not the host or LKL fd) so close-time sync sees the data.forward_sendfile, look upout_fdin the fd table and, whenshadow_writebackandshadow_spare set, route writes toshadow_spwith fallback to LKL/host paths otherwise.sendfile-testto verify data is written through the shadow path and enable it inrun-tests.sh.Written for commit 00002a8. Summary will update on new commits.