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binfmt_misc: restore write access before closing files opened by open_exec()

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bm_register_write() opens an executable file using open_exec(), which
internally calls do_open_execat() and denies write access on the file to
avoid modification while it is being executed.

However, when an error occurs, bm_register_write() closes the file using
filp_close() directly. This does not restore the write permission, which
may cause subsequent write operations on the same file to fail.

Fix this by calling exe_file_allow_write_access() before filp_close() to
restore the write permission properly.

Fixes: e7850f4d84 ("binfmt_misc: fix possible deadlock in bm_register_write")
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Link: https://patch.msgid.link/20251105022923.1813587-1-zilin@seu.edu.cn
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Zilin Guan
2025-11-05 02:29:23 +00:00
committed by Christian Brauner
parent c014021253
commit 90f601b497
1 changed files with 3 additions and 1 deletions
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4
fs/binfmt_misc.c
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@@ -837,8 +837,10 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
inode_unlock(d_inode(root));
if (err) {
if (f)
if (f) {
exe_file_allow_write_access(f);
filp_close(f, NULL);
}
kfree(e);
return err;
}