On Mon, Mar 23, 2026 at 08:31:44PM +0000, Pasha Tatashin wrote: > Currently, LUO does not prevent the same file from being managed twice > across different active sessions. > > Use a global xarray `luo_preserved_files_xa` to keep track of file
Do we really need _xa suffix? > pointers being preserved by LUO. Update luo_preserve_file() to check and > insert the file pointer into this xarray when it is preserved, and > erase it in luo_file_unpreserve_files() when it is released. > > This ensures that the same file (struct file) cannot be managed by > multiple sessions. If another session attempts to preserve an already > managed file, it will now fail with -EBUSY. > > Signed-off-by: Pasha Tatashin <[email protected]> > --- > kernel/liveupdate/luo_file.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c > index a38ea4975824..5f48c3c8c561 100644 > --- a/kernel/liveupdate/luo_file.c > +++ b/kernel/liveupdate/luo_file.c > @@ -110,11 +110,15 @@ > #include <linux/sizes.h> > #include <linux/slab.h> > #include <linux/string.h> > +#include <linux/xarray.h> > #include "luo_internal.h" > > static DECLARE_RWSEM(luo_file_handler_lock); > static LIST_HEAD(luo_file_handler_list); > > +/* Keep track of files being preserved by LUO */ > +static DEFINE_XARRAY(luo_preserved_files_xa); > + > /* 2 4K pages, give space for 128 files per file_set */ > #define LUO_FILE_PGCNT 2ul > #define LUO_FILE_MAX \ > @@ -249,6 +253,7 @@ static bool luo_token_is_used(struct luo_file_set > *file_set, u64 token) > * Context: Can be called from an ioctl handler during normal system > operation. > * Return: 0 on success. Returns a negative errno on failure: > * -EEXIST if the token is already used. > + * -EBUSY if the file descriptor is already preserved by another > session. > * -EBADF if the file descriptor is invalid. > * -ENOSPC if the file_set is full. > * -ENOENT if no compatible handler is found. > @@ -277,6 +282,11 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 > token, int fd) > if (err) > goto err_fput; > > + err = xa_insert(&luo_preserved_files_xa, (unsigned long)file, > + file, GFP_KERNEL); > + if (err) > + goto err_free_files_mem; > + > err = -ENOENT; > scoped_guard(rwsem_read, &luo_file_handler_lock) { > list_private_for_each_entry(fh, &luo_file_handler_list, list) { > @@ -289,11 +299,11 @@ int luo_preserve_file(struct luo_file_set *file_set, > u64 token, int fd) > > /* err is still -ENOENT if no handler was found */ > if (err) > - goto err_free_files_mem; > + goto err_erase_xa; > > err = luo_flb_file_preserve(fh); > if (err) > - goto err_free_files_mem; > + goto err_erase_xa; > > luo_file = kzalloc_obj(*luo_file); > if (!luo_file) { > @@ -323,6 +333,8 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 > token, int fd) > kfree(luo_file); > err_flb_unpreserve: > luo_flb_file_unpreserve(fh); > +err_erase_xa: > + xa_erase(&luo_preserved_files_xa, (unsigned long)file); > err_free_files_mem: > luo_free_files_mem(file_set); > err_fput: > @@ -366,6 +378,7 @@ void luo_file_unpreserve_files(struct luo_file_set > *file_set) > luo_file->fh->ops->unpreserve(&args); > luo_flb_file_unpreserve(luo_file->fh); > > + xa_erase(&luo_preserved_files_xa, (unsigned > long)luo_file->file); > list_del(&luo_file->list); > file_set->count--; > > -- > 2.43.0 > -- Sincerely yours, Mike.
