Change Details

O_SEARCH is defined by POSIX [0] to open a directory for searching, skipping permissions checks on the directory itself. This is in-fact the semantic we've historically applied for O_EXEC on a directory, which is UB according to POSIX. Conveniently, O_SEARCH on a file is also explicitly undefined behavior according to POSIX, so O_EXEC would be a fine choice. The spec goes on to state that O_SEARCH and O_EXEC need not be distinct values, but they're not defined to be the same value. This was pointed out as an incompatibility with other systems that had made its way into libarchive, which had assumed that O_EXEC was an alias for O_SEARCH. [0] https://pubs.opengroup.org/onlinepubs/9699919799/

O_SEARCH is defined by POSIX [0] to open a directory for searching, skipping permissions checks on the directory itself. This is close to the semantics we've historically applied for O_EXEC on a directory, which is UB according to POSIX. Conveniently, O_SEARCH on a file is also explicitly undefined behavior according to POSIX, so O_EXEC would be a fine choice. The spec goes on to state that O_SEARCH and O_EXEC need not be distinct values, but they're not defined to be the same value. This was pointed out as an incompatibility with other systems that had made its way into libarchive, which had assumed that O_EXEC was an alias for O_SEARCH. This defines compatibility O_SEARCH/FSEARCH (equivalent to O_EXEC and FEXEC respectively) and expands our UB for O_EXEC on a directory. O_EXEC on a directory is checked in vn_open_vnode already, so for completeness we add a NOEXECCHECK when O_SEARCH has been specified on the top-level fd and do not re-check that one when descending in namei. [0] https://pubs.opengroup.org/onlinepubs/9699919799/

O_SEARCH is defined by POSIX [0] to open a directory for searching, skipping permissions checks on the directory itself. This is in-factclose to the semantics we've historically applied for O_EXEC on a directory, which is UB according to POSIX. Conveniently, O_SEARCH on a file is also explicitly undefined behavior according to POSIX, so O_EXEC would be a fine choice. The spec goes on to state that O_SEARCH and O_EXEC need not be distinct values, which is UB according to POSIXbut they're not defined to be the same value. Conveniently, O_SEARCH on a file is also explicitly undefined behavior according to POSIX, so O_EXEC would be a fine choice. The spec goes on to state that O_SEARCH and O_EXEC need not be distinct values, but they're not defined to be the same value. This was pointed out as an incompatibility with other systems that had made its way into libarchive, which had assumed that O_EXEC was an alias for O_SEARCH. This defines compatibility O_SEARCH/FSEARCH (equivalent to O_EXEC and FEXEC respectively) and expands our UB for O_EXEC on a directory. O_EXEC on a directory is checked in vn_open_vnode already, so for completeness we add a NOEXECCHECK when O_SEARCH has been specified on the top-level fd and do not re-check that one when descending in namei. [0] https://pubs.opengroup.org/onlinepubs/9699919799/