gnt: Avoid double unmapping on domain cleanup #5
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This resolves the issue I was seeing with PVH unikernels, confirmed in manual testing. |
lindig
approved these changes
Jan 22, 2025
| caml_failwith ("Failed to unmap grant"); | ||
| } | ||
| xengnttab_handle* xgt = _G(xgh); | ||
| void* start_address = _M(array)->addr; |
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Would the code clearer without the alias that we create here for M(array)->addr? So not declaring start_address and using the pointer instead in all places? Because then the NULL-ing becomes more obvious.
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_M accesses an OCaml object, so we need some kind of alias anyway to only access C objects inside the critical section
robhoes
approved these changes
Jan 22, 2025
Oxenstored itself, when cleaning up domains and connections, can call Gnt.unmap transitively several times. Under certain conditions, this can later result in a segfault bringing oxenstored down when it tries to use a freed grant. Set the mmap_interface pointer to NULL after the first attempt so that it can be detected on the subsequent ones. Since we are already at it, bring out accesses to OCaml fields out of the critical section. Signed-off-by: Andrii Sultanov <[email protected]>
stub_gnttab_map_fresh Signed-off-by: Andrii Sultanov <[email protected]>
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Addressed the suggestions, retested - looks good. |
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Oxenstored itself, when cleaning up domains and connections, can call Gnt.unmap transitively several times. Under certain conditions, this can later result in a segfault bringing oxenstored down when it tries to use a freed grant.
Set the mmap_interface pointer to NULL after the first attempt so that it can be detected on the subsequent ones.
Since we are already at it, bring out accesses to OCaml fields out of the critical section.