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Subject[PATCH][next] ima: ima_modsig: Fix use-after-free bug in ima_read_modsig
hdr is being freed and then dereferenced by accessing hdr->pkcs7_msg

Fix this by copying the value returned by PTR_ERR(hdr->pkcs7_msg) into
automatic variable err for its safe use after freeing hdr.

Addresses-Coverity-ID: 1485813 ("Read from pointer after free")
Fixes: 39b07096364a ("ima: Implement support for module-style appended signatures")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
security/integrity/ima/ima_modsig.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c
index c412e31d1714..e681d4326145 100644
--- a/security/integrity/ima/ima_modsig.c
+++ b/security/integrity/ima/ima_modsig.c
@@ -91,8 +91,9 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len,

hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len);
if (IS_ERR(hdr->pkcs7_msg)) {
+ int err = PTR_ERR(hdr->pkcs7_msg);
kfree(hdr);
- return PTR_ERR(hdr->pkcs7_msg);
+ return err;
}

memcpy(hdr->raw_pkcs7, buf + buf_len, sig_len);
--
2.22.0
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