This is a note to let you know that I've just added the patch titled
btrfs: fix signed overflows in btrfs_sync_file
to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
btrfs-fix-signed-overflows-in-btrfs_sync_file.patch
and it can be found in the queue-4.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 9dcbeed4d7e11e1dcf5e55475de3754f0855d1c2 Mon Sep 17 00:00:00 2001
From: David Sterba <[email protected]>
Date: Mon, 9 Nov 2015 11:44:45 +0100
Subject: btrfs: fix signed overflows in btrfs_sync_file
From: David Sterba <[email protected]>
commit 9dcbeed4d7e11e1dcf5e55475de3754f0855d1c2 upstream.
The calculation of range length in btrfs_sync_file leads to signed
overflow. This was caught by PaX gcc SIZE_OVERFLOW plugin.
https://forums.grsecurity.net/viewtopic.php?f=1&t=4284
The fsync call passes 0 and LLONG_MAX, the range length does not fit to
loff_t and overflows, but the value is converted to u64 so it silently
works as expected.
The minimal fix is a typecast to u64, switching functions to take
(start, end) instead of (start, len) would be more intrusive.
Coccinelle script found that there's one more opencoded calculation of
the length.
<smpl>
@@
loff_t start, end;
@@
* end - start
</smpl>
Signed-off-by: David Sterba <[email protected]>
Signed-off-by: Chris Mason <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
fs/btrfs/file.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1876,8 +1876,13 @@ int btrfs_sync_file(struct file *file, l
struct btrfs_log_ctx ctx;
int ret = 0;
bool full_sync = 0;
- const u64 len = end - start + 1;
+ u64 len;
+ /*
+ * The range length can be represented by u64, we have to do the
typecasts
+ * to avoid signed overflow if it's [0, LLONG_MAX] eg. from fsync()
+ */
+ len = (u64)end - (u64)start + 1;
trace_btrfs_sync_file(file, datasync);
/*
@@ -2065,8 +2070,7 @@ int btrfs_sync_file(struct file *file, l
}
}
if (!full_sync) {
- ret = btrfs_wait_ordered_range(inode, start,
- end - start + 1);
+ ret = btrfs_wait_ordered_range(inode, start, len);
if (ret) {
btrfs_end_transaction(trans, root);
goto out;
Patches currently in stable-queue which might be from [email protected] are
queue-4.2/btrfs-check-unsupported-filters-in-balance-arguments.patch
queue-4.2/btrfs-fix-signed-overflows-in-btrfs_sync_file.patch
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