tjh.dev / kernel
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ntfs: fix uninitialized pointer in ntfs_write_mft_block

Smatch reported that the variable rl could be used uninitialized in
ntfs_write_mft_block(). After analyzing the code,
when vol->cluster_size == NTFS_BLOCK_SIZE (512), it is smaller than
folio_size, so rl is guaranteed to be initialized. If vol->cluster_size
is larger, the condition to access rl becomes false, so a runtime error is
not expected to occur. However, to make the static checker happy,
this patch initializes rl to NULL and adds an explicit check before
its usage.

Reported-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Namjae Jeon 545834ac 8a59a2d8

+2 -2
+2 -2
fs/ntfs/mft.c
··· 2714 2714 s64 vcn = ntfs_pidx_to_cluster(vol, folio->index); 2715 2715 s64 end_vcn = ntfs_bytes_to_cluster(vol, ni->allocated_size); 2716 2716 unsigned int folio_sz; 2717 - struct runlist_element *rl; 2717 + struct runlist_element *rl = NULL; 2718 2718 loff_t i_size = i_size_read(vi); 2719 2719 2720 2720 ntfs_debug("Entering for inode 0x%llx, attribute type 0x%x, folio index 0x%lx.", ··· 2820 2820 2821 2821 if (vol->cluster_size == NTFS_BLOCK_SIZE && 2822 2822 (mft_record_off || 2823 - rl->length - (vcn_off - rl->vcn) == 1 || 2823 + (rl && rl->length - (vcn_off - rl->vcn) == 1) || 2824 2824 mft_ofs + NTFS_BLOCK_SIZE >= PAGE_SIZE)) 2825 2825 folio_sz = NTFS_BLOCK_SIZE; 2826 2826 else