CVE-2026-74486binfmt_misc: use exe_file_deny_write_access() for the interpreter clone

Official description

In the Linux kernel, the following vulnerability has been resolved: binfmt_misc: use exe_file_deny_write_access() for the interpreter clone For MISC_FMT_OPEN_FILE entries load_misc_binary() clones the registered interpreter file and denies write access to the clone via plain deny_write_access(). The clone is installed as bprm->interpreter and later released by the exec machinery through exe_file_allow_write_access() which skips the i_writecount increment for files with FMODE_FSNOTIFY_HSM set. The deny and allow side can therefore come to different conclusions when pre-content watches are in play: if a pre-content watch is added to the interpreter after registration every subsequent exec through that entry takes a write denial on the clone that is never paired with a write allowance, driving the interpreter inode's i_writecount further down with each exec and leaving the interpreter unwritable even after the entry and all its users are gone. Take the write denial via exe_file_deny_write_access() so both sides of the pairing base their decision on the same file mode, and propagate failure instead of silently ignoring it: an interpreter that is concurrently open for writing now fails the exec with ETXTBSY, exactly like an interpreter freshly opened via open_exec() would.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/c65eb018c12179b5e2c7afe1f0956298576fecec
• https://git.kernel.org/stable/c/2bd860b7e752a51185960143cab9fec7bf32c84e
• https://git.kernel.org/stable/c/eea4b7c7711b1e425272d23352af157f45f4c3e3
• https://git.kernel.org/stable/c/2fdf8b07bee5ef99ec77773a6be05fbb8ee5cdb9
• https://git.kernel.org/stable/c/f1e7ea3c8e070f19771cdaef55bbeda1359ad490
• https://git.kernel.org/stable/c/255a758697da87a205e072e0cfc35897b8f743b1
• https://git.kernel.org/stable/c/f0edbaf487e4653a680a7abb91c1df94cb7886aa
• https://git.kernel.org/stable/c/fa5990ca8fd917003e526036bcc50413edb9722c