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80 lines
2.6 KiB
80 lines
2.6 KiB
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Notes on the change from 16-bit UIDs to 32-bit UIDs |
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:Author: Chris Wing <[email protected]> |
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:Last updated: January 11, 2000 |
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- kernel code MUST take into account __kernel_uid_t and __kernel_uid32_t |
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when communicating between user and kernel space in an ioctl or data |
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structure. |
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- kernel code should use uid_t and gid_t in kernel-private structures and |
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code. |
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What's left to be done for 32-bit UIDs on all Linux architectures: |
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- Disk quotas have an interesting limitation that is not related to the |
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maximum UID/GID. They are limited by the maximum file size on the |
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underlying filesystem, because quota records are written at offsets |
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corresponding to the UID in question. |
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Further investigation is needed to see if the quota system can cope |
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properly with huge UIDs. If it can deal with 64-bit file offsets on all |
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architectures, this should not be a problem. |
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- Decide whether or not to keep backwards compatibility with the system |
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accounting file, or if we should break it as the comments suggest |
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(currently, the old 16-bit UID and GID are still written to disk, and |
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part of the former pad space is used to store separate 32-bit UID and |
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GID) |
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- Need to validate that OS emulation calls the 16-bit UID |
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compatibility syscalls, if the OS being emulated used 16-bit UIDs, or |
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uses the 32-bit UID system calls properly otherwise. |
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This affects at least: |
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- iBCS on Intel |
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- sparc32 emulation on sparc64 |
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(need to support whatever new 32-bit UID system calls are added to |
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sparc32) |
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- Validate that all filesystems behave properly. |
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At present, 32-bit UIDs _should_ work for: |
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- ext2 |
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- ufs |
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- isofs |
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- nfs |
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- coda |
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- udf |
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Ioctl() fixups have been made for: |
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- ncpfs |
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- smbfs |
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Filesystems with simple fixups to prevent 16-bit UID wraparound: |
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- minix |
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- sysv |
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- qnx4 |
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Other filesystems have not been checked yet. |
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- The ncpfs and smpfs filesystems cannot presently use 32-bit UIDs in |
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all ioctl()s. Some new ioctl()s have been added with 32-bit UIDs, but |
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more are needed. (as well as new user<->kernel data structures) |
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- The ELF core dump format only supports 16-bit UIDs on arm, i386, m68k, |
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sh, and sparc32. Fixing this is probably not that important, but would |
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require adding a new ELF section. |
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- The ioctl()s used to control the in-kernel NFS server only support |
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16-bit UIDs on arm, i386, m68k, sh, and sparc32. |
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- make sure that the UID mapping feature of AX25 networking works properly |
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(it should be safe because it's always used a 32-bit integer to |
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communicate between user and kernel)
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