From: Huiwen He <hehuiwen@kylinos.cn> mainline inclusion from mainline-v7.2-rc4 commit b09ae45d85dc816987a71db9eebc54b0ae288e94 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/17070 CVE: CVE-2026-68388 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- smb3_simple_fallocate_range() can skip holes when an allocated range returned by the server starts before the current fallocate offset. The skipped hole is not zero-filled, but fallocate still returns success. A later write to that hole may therefore fail with ENOSPC. The function queries allocated ranges so that it can preserve existing contents and write zeroes only into holes. However, the server may return a range that starts before the current fallocate offset. For example, assume the fallocate request is [100, 400) and the only allocated range returned by the server is [0, 200): Request: [100, 400) Server range: [ 0, 200) allocated Correct: [100, 200) allocated data, skip [200, 400) hole, zero-fill Current: [100, 300) skipped [300, 400) zero-filled afterwards The current code adds the full server range length, 200, to the current offset 100 and moves to 300. As a result, the hole in [200, 300) is skipped without being zero-filled. Fix this by advancing only over the part of the allocated range that overlaps the current fallocate offset. Ignore ranges that end before the current offset and reject ranges whose end offset overflows. This also prevents a malformed range length from causing an out-of-bounds zero-buffer read. Fixes: 966a3cb7c7db ("cifs: improve fallocate emulation") Signed-off-by: Huiwen He <hehuiwen@kylinos.cn> Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn> Signed-off-by: Steve French <stfrench@microsoft.com> Signed-off-by: Lu Chentao <luchentao1@huawei.com> --- fs/cifs/smb2ops.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index f46c99b61c04..dd72160a4bb4 100644 --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -3561,10 +3561,11 @@ static int smb3_simple_fallocate_range(unsigned int xid, loff_t off, loff_t len) { struct file_allocated_range_buffer in_data, *out_data = NULL, *tmp_data; u32 out_data_len; char *buf = NULL; + u64 range_start, range_len, range_end; loff_t l; int rc; in_data.file_offset = cpu_to_le64(off); in_data.length = cpu_to_le64(len); @@ -3597,17 +3598,25 @@ static int smb3_simple_fallocate_range(unsigned int xid, if (out_data_len < sizeof(struct file_allocated_range_buffer)) { rc = -EINVAL; goto out; } - if (off < le64_to_cpu(tmp_data->file_offset)) { + range_start = le64_to_cpu(tmp_data->file_offset); + range_len = le64_to_cpu(tmp_data->length); + if (check_add_overflow(range_start, range_len, &range_end) || + range_end > S64_MAX) { + rc = -EINVAL; + goto out; + } + + if (off < range_start) { /* * We are at a hole. Write until the end of the region * or until the next allocated data, * whichever comes next. */ - l = le64_to_cpu(tmp_data->file_offset) - off; + l = range_start - off; if (len < l) l = len; rc = smb3_simple_fallocate_write_range(xid, tcon, cfile, off, l, buf); if (rc) @@ -3620,15 +3629,17 @@ static int smb3_simple_fallocate_range(unsigned int xid, /* * We are at a section of allocated data, just skip forward * until the end of the data or the end of the region * we are supposed to fallocate, whichever comes first. */ - l = le64_to_cpu(tmp_data->length); - if (len < l) - l = len; - off += l; - len -= l; + if (off < range_end) { + l = range_end - off; + if (len < l) + l = len; + off += l; + len -= l; + } tmp_data = &tmp_data[1]; out_data_len -= sizeof(struct file_allocated_range_buffer); } -- 2.52.0