On Mon, Mar 24, 2025 at 09:23:53AM -0700, Penglei Jiang wrote: > The following functions call proc_mem_open but do not handle the case > where it returns NULL: > > __mem_open in fs/proc/base.c > proc_maps_open in fs/proc/task_mmu.c > smaps_rollup_open in fs/proc/task_mmu.c > pagemap_open in fs/proc/task_mmu.c > maps_open in fs/proc/task_nommu.c > > The following reported bugs may be related to this issue: > > https://lore.kernel.org/all/000000000000f52642060d4e3750@xxxxxxxxxx > https://lore.kernel.org/all/0000000000001bc4a00612d9a7f4@xxxxxxxxxx > > Fix: > > Modify proc_mem_open to return an error code in case of errors, instead > of returning NULL. > The rw routines associated with these consumers explictly NULL check mm, which becomes redundant with the patch. While I find it fishy that returning NULL was ever a thing to begin with, it is unclear to me if it can be easily changed now from userspace-visible behavior standpoint. I think the best way forward for the time being is to add the missing NULL checks instead. > Signed-off-by: Penglei Jiang <superman.xpt@xxxxxxxxx> > --- > fs/proc/base.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index cd89e956c322..b5e7317cf0dc 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -840,7 +840,7 @@ struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode) > put_task_struct(task); > > if (IS_ERR(mm)) > - return mm == ERR_PTR(-ESRCH) ? NULL : mm; > + return mm; > > /* ensure this mm_struct can't be freed */ > mmgrab(mm); > -- > 2.17.1 >
