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tmpfs: limit regularFile.Translate() fill range #11343

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Merged
merged 1 commit into from
Jan 8, 2025
Merged

tmpfs: limit regularFile.Translate() fill range #11343

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13 changes: 13 additions & 0 deletions pkg/sentry/fsimpl/tmpfs/regular_file.go
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Original file line number Diff line number Diff line change
Expand Up @@ -309,6 +309,19 @@ func (rf *regularFile) Translate(ctx context.Context, required, optional memmap.
if optional.End > pgend {
optional.End = pgend
}
// Constrain allocation to at most maxOptionalBytes or required.Length(),
// whichever is greater.
const maxOptionalBytes = 64 << 10 // 64 KB, arbitrarily matches Linux's default fault_around_pages
if required.Length() >= maxOptionalBytes {
optional = required
} else {
if optional.Length() > maxOptionalBytes {
optional.Start = required.Start
if optional.Length() > maxOptionalBytes {
optional.End = optional.Start + maxOptionalBytes
}
}
}
pagesToFill := rf.data.PagesToFill(required, optional)
if !rf.inode.fs.accountPages(pagesToFill) {
// If we can not accommodate pagesToFill pages, then retry with just
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