[PATCH v2 3/8] fs: btrfs: fix a crash if specified range is beyond file size
Qu Wenruo
wqu at suse.com
Tue Jul 26 07:22:11 CEST 2022
[BUG]
When try to read a range beyond file size, btrfs driver will cause
crash/segfault:
=> load host 0 $kernel_addr_r 5k_file 0 0x2000
SEGFAULT
[CAUSE]
In btrfs_read(), if @len is 0, we will truncated it to file end, but if
file end is beyond our file size, this truncation will underflow @len,
making it -3K in this case.
And later that @len is used to memzero the output buffer, resulting
above crash.
[FIX]
Just error out if @offset is already beyond our file size.
Now it will fail properly with correct error message:
=> load host 0 $kernel_addr_r 5m_origin 0 0x2000
BTRFS: Read range beyond file size, offset 8192 file size 5120
Failed to load '5m_origin'
Signed-off-by: Qu Wenruo <wqu at suse.com>
---
fs/btrfs/btrfs.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/btrfs/btrfs.c b/fs/btrfs/btrfs.c
index 9145727058d4..bf9e1f2f17cf 100644
--- a/fs/btrfs/btrfs.c
+++ b/fs/btrfs/btrfs.c
@@ -252,6 +252,12 @@ int btrfs_read(const char *file, void *buf, loff_t offset, loff_t len,
return ret;
}
+ if (offset >= real_size) {
+ error("Read range beyond file size, offset %llu file size %llu",
+ offset, real_size);
+ return -EINVAL;
+ }
+
/*
* If the length is 0 (meaning read the whole file) or the range is
* beyond file size, truncate it to the end of the file.
--
2.37.0
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