From 4a5950a1298aedabe2cf730c5dc9d36cebbef79c Mon Sep 17 00:00:00 2001 From: Richard Yao Date: Wed, 1 Mar 2023 16:19:47 -0500 Subject: [PATCH] Linux: zfs_fillpage() should handle partial pages from end of file After 89cd2197b94986d315b9b1be707b645baf59af4f was merged, Clang's static analyzer began complaining about a dead assignment in `zfs_fillpage()`. Upon inspection, I noticed that the dead assignment was because we are not using the calculated io_len that we should use to avoid asking the DMU to read past the end of a file. This should result in `dmu_buf_hold_array_by_dnode()` calling `zfs_panic_recover()`. This issue predates 89cd2197b94986d315b9b1be707b645baf59af4f, but its simplification of zfs_fillpage() eliminated the only use of the assignment to io_len, which made Clang's static analyzer complain about the issue. Also, as a precaution, we add an assertion that io_offset < i_size. If this ever fails, bad things will happen. Otherwise, we are blindly trusting the kernel not to give us invalid offsets. We continue to blindly trust it on non-debug kernels. Reviewed-by: Brian Behlendorf Reviewed-by: Brian Atkinson Signed-off-by: Richard Yao Closes #14534 --- module/os/linux/zfs/zfs_vnops_os.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/module/os/linux/zfs/zfs_vnops_os.c b/module/os/linux/zfs/zfs_vnops_os.c index 27e1ab420bb7..c171448080cd 100644 --- a/module/os/linux/zfs/zfs_vnops_os.c +++ b/module/os/linux/zfs/zfs_vnops_os.c @@ -3784,12 +3784,16 @@ zfs_fillpage(struct inode *ip, struct page *pp) u_offset_t io_off = page_offset(pp); size_t io_len = PAGE_SIZE; + ASSERT3U(io_off, <, i_size); + if (io_off + io_len > i_size) io_len = i_size - io_off; void *va = kmap(pp); int error = dmu_read(zfsvfs->z_os, ITOZ(ip)->z_id, io_off, - PAGE_SIZE, va, DMU_READ_PREFETCH); + io_len, va, DMU_READ_PREFETCH); + if (io_len != PAGE_SIZE) + memset((char *)va + io_len, 0, PAGE_SIZE - io_len); kunmap(pp); if (error) {