On Wed, Sep 29, 2021 at 04:23:39PM +0530, Shreeya Patel wrote: > /proc/self/cwd is a symlink created by the kernel that uses whatever > name the dentry has in the dcache. Since the dcache is populated only > on the first lookup, with the string used in that lookup, cwd will > have an unexpected case, depending on how the data was first looked-up > in a case-insesitive filesystem. > > Steps to reproduce :- > > root@test-box:/src# mkdir insensitive/foo > root@test-box:/src# cd insensitive/FOO > root@test-box:/src/insensitive/FOO# ls -l /proc/self/cwd > lrwxrwxrwx 1 root root /proc/self/cwd -> /src/insensitive/FOO > > root@test-box:/src/insensitive/FOO# cd ../fOo > root@test-box:/src/insensitive/fOo# ls -l /proc/self/cwd > lrwxrwxrwx 1 root root /proc/self/cwd -> /src/insensitive/FOO > > Above example shows that 'FOO' was the name used on first lookup here and > it is stored in dcache instead of the original name 'foo'. This results > in inconsistent name exposed by /proc/self/cwd since it uses the name > stored in dcache. > > To avoid the above inconsistent name issue, handle the inexact-match string > ( a string which is not a byte to byte match, but is an equivalent > unicode string ) case in ext4_lookup which would store the original name > in dcache using d_add_ci instead of the inexact-match string name. I'm not sure this is a problem. /proc/<pid>/cwd just needs to point at the current working directory for the process. Why do we care whether it matches the case that was stored on disk? Whether we use /src/insensitive/FOO, or /src/insensitive/Foo, or /src/insensitive/foo, all of these will reach the cwd for that process. - Ted
