mremap_after_coalesce fails, both with and without rr
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Description
On my system, I get:
mmap(NULL, 143360, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7ffff7fad000
mmap(0x7ffff7fad000, 4096, PROT_READ, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x7ffff7fad000
mremap(0x7ffff7fad000, 143360, 147456, MREMAP_MAYMOVE) = -1 EFAULT (Bad address)
Looking at the mremap manpage, it doesn't seem that I should be getting an error unless the mappings "are of different types". They're not, as far as I can tell.
This is a Debian system, and Debian appears to configure some kernel parameters differently from other distributions, but I have no idea what to look for.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing the mremap_after_coalesce failure on the reported Debian system, both with and without rr, using the mmap and mremap sequence in the report. Read the Linux mremap behavior and compare the mapping types and kernel configuration involved. Done means explaining the EFAULT and adding or updating a regression check for the failure.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp, linux
- Domain
- operating-systems
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100