[PATCH] IMA: Mask O_RDWR if FMODE_READ is set

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A file can be opened with open(O_WRONLY | O_RDWR), so a FMORE_READ
will not be set, and overlayfs will consider another copy_up() on the same
file leading to a deadlock on mnt_want_write(). Fix it by masking
O_RDWR while opening the file in read-only mode.


Reported-by: syzbot+ae82084b07d0297e566b@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: a408e4a86b36 ("ima: open a new file instance if no read permissions")
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>

diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index d9e7728027c6..2efa04e47ff0 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -422,7 +422,7 @@ int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
 	/* Open a new file instance in O_RDONLY if we cannot read */
 	if (!(file->f_mode & FMODE_READ)) {
 		int flags = file->f_flags & ~(O_WRONLY | O_APPEND |
-				O_TRUNC | O_CREAT | O_NOCTTY | O_EXCL);
+				O_RDWR | O_TRUNC | O_CREAT | O_NOCTTY | O_EXCL);
 		flags |= O_RDONLY;
 		f = dentry_open(&file->f_path, flags, file->f_cred);
 		if (IS_ERR(f)) {

-- 
Goldwyn



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