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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH] keys: Fix proc_keys_next to increase position index From: David Howells To: torvalds@linux-foundation.org Cc: stable@vger.kernel.org, Vasily Averin , dhowells@redhat.com, jarkko.sakkinen@linux.intel.com, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 14 Apr 2020 21:33:16 +0100 Message-ID: <158689639664.3925765.4549426529245164675.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.21 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: keyrings-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: keyrings@vger.kernel.org From: Vasily Averin If seq_file .next function does not change position index, read after some lseek can generate unexpected output: $ dd if=/proc/keys bs=1 # full usual output 0f6bfdf5 I--Q--- 2 perm 3f010000 1000 1000 user 4af2f79ab8848d0a: 740 1fb91b32 I--Q--- 3 perm 1f3f0000 1000 65534 keyring _uid.1000: 2 27589480 I--Q--- 1 perm 0b0b0000 0 0 user invocation_id: 16 2f33ab67 I--Q--- 152 perm 3f030000 0 0 keyring _ses: 2 33f1d8fa I--Q--- 4 perm 3f030000 1000 1000 keyring _ses: 1 3d427fda I--Q--- 2 perm 3f010000 1000 1000 user 69ec44aec7678e5a: 740 3ead4096 I--Q--- 1 perm 1f3f0000 1000 65534 keyring _uid_ses.1000: 1 521+0 records in 521+0 records out 521 bytes copied, 0,00123769 s, 421 kB/s $ dd if=/proc/keys bs=500 skip=1 # read after lseek in middle of last line dd: /proc/keys: cannot skip to specified offset g _uid_ses.1000: 1 <<<< end of last line 3ead4096 I--Q--- 1 perm 1f3f0000 1000 65534 keyring _uid_ses.1000: 1 <<<< and whole last line again 0+1 records in 0+1 records out 97 bytes copied, 0,000135035 s, 718 kB/s $ dd if=/proc/keys bs=1000 skip=1 # read after lseek beyond end of file dd: /proc/keys: cannot skip to specified offset 3ead4096 I--Q--- 1 perm 1f3f0000 1000 65534 keyring _uid_ses.1000: 1 <<<< generates last line 0+1 records in 0+1 records out 76 bytes copied, 0,000119981 s, 633 kB/s See https://bugzilla.kernel.org/show_bug.cgi?id=206283 Cc: stable@vger.kernel.org Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code ...") Signed-off-by: Vasily Averin Signed-off-by: David Howells Reviewed-by: Jarkko Sakkinen --- security/keys/proc.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/security/keys/proc.c b/security/keys/proc.c index 415f3f1c2da0..d0cde6685627 100644 --- a/security/keys/proc.c +++ b/security/keys/proc.c @@ -139,6 +139,8 @@ static void *proc_keys_next(struct seq_file *p, void *v, loff_t *_pos) n = key_serial_next(p, v); if (n) *_pos = key_node_serial(n); + else + (*_pos)++; return n; }