From: Liu Bo <bo.li.liu@oracle.com>
Date: Tue, 16 Sep 2014 17:49:30 +0800
Subject: [PATCH] Btrfs: fix up bounds checking in lseek
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(cherry picked from commit 4d1a40c66bed0b3fa43b9da5fbd5cbe332e4eccf)
An user reported this, it is because that lseek's SEEK_SET/SEEK_CUR/SEEK_END
allow a negative value for @offset, but btrfs's SEEK_DATA/SEEK_HOLE don't
prepare for that and convert the negative @offset into unsigned type,
so we get (end < start) warning.
[ 1269.835374] ------------[ cut here ]------------
[ 1269.836809] WARNING: CPU: 0 PID: 1241 at fs/btrfs/extent_io.c:430 insert_state+0x11d/0x140()
[ 1269.838816] BTRFS: end < start 4094 18446744073709551615
[ 1269.840334] CPU: 0 PID: 1241 Comm: a.out Tainted: G W 3.16.0+ #306
[ 1269.858229] Call Trace:
[ 1269.858612] [<ffffffff81801a69>] dump_stack+0x4e/0x68
[ 1269.858952] [<ffffffff8107894c>] warn_slowpath_common+0x8c/0xc0
[ 1269.859416] [<ffffffff81078a36>] warn_slowpath_fmt+0x46/0x50
[ 1269.859929] [<ffffffff813b0fbd>] insert_state+0x11d/0x140
[ 1269.860409] [<ffffffff813b1396>] __set_extent_bit+0x3b6/0x4e0
[ 1269.860805] [<ffffffff813b21c7>] lock_extent_bits+0x87/0x200
[ 1269.861697] [<ffffffff813a5b28>] btrfs_file_llseek+0x148/0x2a0
[ 1269.862168] [<ffffffff811f201e>] SyS_lseek+0xae/0xc0
[ 1269.862620] [<ffffffff8180b212>] system_call_fastpath+0x16/0x1b
[ 1269.862970] ---[ end trace 4d33ea885832054b ]---
This assumes that btrfs starts finding DATA/HOLE from the beginning of file
if the assigned @offset is negative.
Also we add alignment for lock_extent_bits 's range.
Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <clm@fb.com>
---
fs/btrfs/file.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ff1cc0399b9a..68dd92cd7d54 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2621,23 +2621,28 @@ static int find_desired_extent(struct inode *inode, loff_t *offset, int whence)
struct btrfs_root *root = BTRFS_I(inode)->root;
struct extent_map *em = NULL;
struct extent_state *cached_state = NULL;
- u64 lockstart = *offset;
- u64 lockend = i_size_read(inode);
- u64 start = *offset;
- u64 len = i_size_read(inode);
+ u64 lockstart;
+ u64 lockend;
+ u64 start;
+ u64 len;
int ret = 0;
- lockend = max_t(u64, root->sectorsize, lockend);
+ if (inode->i_size == 0)
+ return -ENXIO;
+
+ /*
+ * *offset can be negative, in this case we start finding DATA/HOLE from
+ * the very start of the file.
+ */
+ start = max_t(loff_t, 0, *offset);
+
+ lockstart = round_down(start, root->sectorsize);
+ lockend = round_up(i_size_read(inode), root->sectorsize);
if (lockend <= lockstart)
lockend = lockstart + root->sectorsize;
-
lockend--;
len = lockend - lockstart + 1;
- len = max_t(u64, len, root->sectorsize);
- if (inode->i_size == 0)
- return -ENXIO;
-
lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend, 0,
&cached_state);
--
1.9.3