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fs/ntfs3: prevent potential lcn remains uninitialized

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The target VCN being sought was not found within runs[0], causing
run_lookup() to return false. This causes run_lookup_entry() to return
false, which in turn results in a len value of 0, and the new parameter
passed to attr_data_get_block() is NULL. Collectively, these factors
ultimately cause attr_data_get_block_locked() to exit prematurely without
initializing lcn, thereby triggering [1].

To prevent [1], the clen check within ni_seek_data_or_hole() has been
moved to occur before the lcn check.

[1]
BUG: KMSAN: uninit-value in ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ntfs_llseek+0x22a/0x4a0 fs/ntfs3/file.c:1530
 vfs_llseek fs/read_write.c:391 [inline]

Fixes: c613269677 ("fs/ntfs3: implement llseek SEEK_DATA/SEEK_HOLE by scanning data runs")
Reported-by: syzbot+c2cfe997245202e46f10@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c2cfe997245202e46f10
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
This commit is contained in:
Edward Adam Davis 2026-05-26 16:08:04 +08:00 committed by Konstantin Komarov
parent 9611f64430
commit 57ac2831c8
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1 changed files with 5 additions and 4 deletions
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9
fs/ntfs3/frecord.c
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@ -2859,6 +2859,11 @@ loff_t ni_seek_data_or_hole(struct ntfs_inode *ni, loff_t offset, bool data)
return err;
}
if (!clen) {
/* Corrupted file. */
return -EINVAL;
}
if (lcn == RESIDENT_LCN) {
/* clen - resident size in bytes. clen == ni->vfs_inode.i_size */
if (offset >= clen) {
@ -2915,10 +2920,6 @@ loff_t ni_seek_data_or_hole(struct ntfs_inode *ni, loff_t offset, bool data)
}
}
if (!clen) {
/* Corrupted file. */
return -EINVAL;
}
}
vbo = (u64)vcn << cluster_bits;