linux-kernel - [PATCH V7 1/2] mm: fadvise: move 'endbyte' calculations to helper function

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 14 Feb 2023 18:21:49 +0530
From:   Charan Teja Kalla <quic_charante@...cinc.com>
To:     <akpm@...ux-foundation.org>, <hughd@...gle.com>,
        <willy@...radead.org>, <markhemm@...glemail.com>,
        <rientjes@...gle.com>, <surenb@...gle.com>, <shakeelb@...gle.com>,
        <quic_pkondeti@...cinc.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Charan Teja Kalla <quic_charante@...cinc.com>
Subject: [PATCH V7 1/2] mm: fadvise: move 'endbyte' calculations to helper function

Move the 'endbyte' calculations that determines last byte that fadvise
can to a helper function. This is a preparatory change made for
shmem_fadvise() functionality in the next patch. No functional changes
in this patch.

Signed-off-by: Charan Teja Kalla <quic_charante@...cinc.com>
---
 mm/fadvise.c  | 11 +----------
 mm/internal.h | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/mm/fadvise.c b/mm/fadvise.c
index fb7c5f4..1b3cac5 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -65,16 +65,7 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 		return 0;
 	}
 
-	/*
-	 * Careful about overflows. Len == 0 means "as much as possible".  Use
-	 * unsigned math because signed overflows are undefined and UBSan
-	 * complains.
-	 */
-	endbyte = (u64)offset + (u64)len;
-	if (!len || endbyte < len)
-		endbyte = LLONG_MAX;
-	else
-		endbyte--;		/* inclusive */
+	endbyte = fadvise_calc_endbyte(offset, len);
 
 	switch (advice) {
 	case POSIX_FADV_NORMAL:
diff --git a/mm/internal.h b/mm/internal.h
index dfb37e9..4445e48 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -657,6 +657,27 @@ static inline void vunmap_range_noflush(unsigned long start, unsigned long end)
 }
 #endif /* !CONFIG_MMU */
 
+/*
+ * Helper function to get the endbyte of a file that fadvise can operate on.
+ */
+static inline loff_t fadvise_calc_endbyte(loff_t offset, loff_t len)
+{
+	loff_t endbyte;
+
+	/*
+	 * Careful about overflows. Len == 0 means "as much as possible".  Use
+	 * unsigned math because signed overflows are undefined and UBSan
+	 * complains.
+	 */
+	endbyte = (u64)offset + (u64)len;
+	if (!len || endbyte < len)
+		endbyte = LLONG_MAX;
+	else
+		endbyte--;		/* inclusive */
+
+	return endbyte;
+}
+
 /* Memory initialisation debug and verification */
 enum mminit_level {
 	MMINIT_WARNING,
-- 
2.7.4