fat_path2dirname() marks a parsed name as needing long file name
entries by clearing the first byte of the short name buffer, and
fat_dirnamewrite() writes the long name entries only while that marker
survives. Since commit bc9e1ffb01, a name short enough to fit the 8.3
form is speculatively re-parsed as a short name, and the re-parse
fills the short name buffer with spaces before it examines a single
character. When it then rejects the name (lower case, for example) the
spaces stay behind, the marker is gone, and the file is created with
eleven spaces for a name: no long name entries, a blank alias.
Every such file aliases to every other, since every rejected name
converts to the same blank entry. Create a.txt, then create big1, and
both names now open one file; a directory of them lists as a single
nameless entry. Any application that writes two lowercase short-named
files and reads the first back gets the second's contents.
Restore the marker when the speculative parse fails.
Tested on FAT32 with CONFIG_FAT_LFN: lower case, upper case, mixed
case and over-length names now create distinct, correctly named
entries that survive unmount and reboot; upper case 8.3 names still
produce plain short entries with no long name chain.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Justin Hammond <justin@dynam.ac>
8f23897d03