lib/idmapping.c: Fix get_map_ranges regression #1117
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alejandro-colomar
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(I've approved it, but it's really waiting for the commit message update.) |
The get_map_ranges function shall support the whole accepted range as specified in user_namespaces(7), i.e. upper and lower from 0 to UINT_MAX - 1 as well as range from 1 to UINT_MAX. The actual limit of range depends on values of upper and lower and adding the range to either upper or lower shall never overflow UINT_MAX. Fixes: 7c43eb2 (2024-07-11, "lib/idmapping.c: get_map_ranges(): Move range check to a2ul() call") Fixes: ff2baed (2016-08-14, "idmapping: add more checks for overflow") Fixes: 94da3dc (2016-08-14, "also check upper for wrap") Fixes: 7f5a148 (2016-07-31, "get_map_ranges: check for overflow") Co-authored-by: Alejandro Colomar <alx@kernel.org> Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org> Signed-off-by: Alejandro Colomar <alx@kernel.org>
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Almost just in time ... ;) |
:) Thanks! I'll merge. |
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I'm happy that refactoring/simplifying the old code, even though it introduced a bug, it made it more readable and obvious that the previous code was bad, and we've been able to improve the checks beyond what was before my regression. :) |
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If get_map_ranges is called on a 32 bit system, where UINT_MAX equals ULONG_MAX, the count check allows illegal values if uid and loweruid are both UINT_MAX due to unsigned integer underflow.
Always use the fix size UINT_MAX as count limitation due to guarantee that sizeof(unsigned int) <= sizeof(unsigned long) in C language.
Fixes: 7c43eb2 ("lib/idmapping.c: get_map_ranges(): Move range check to a2ul() call")
Proof of Concept (32 bit system):
Output:
Expected: