Messages in this thread | | | Date | Tue, 24 Aug 2021 12:28:07 +0200 | From | Len Baker <> | Subject | Re: [PATCH v4] EDAC/mc: Prefer strscpy over strcpy |
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Hi Borislav,
On Mon, Aug 23, 2021 at 07:30:34PM +0200, Borislav Petkov wrote: > On Sat, Aug 14, 2021 at 09:55:27AM +0200, Len Baker wrote: > > strcpy() performs no bounds checking on the destination buffer. This > > could result in linear overflows beyond the end of the buffer, leading > > to all kinds of misbehaviors. The safe replacement is strscpy(). > > > > This is a previous step in the path to remove the strcpy() function > > "previous step"?
This is a task of the KSPP [1] and the main reason is to clean up the proliferation of str*cpy functions in the kernel.
[1] https://github.com/KSPP/linux/issues/88
> > entirely from the kernel. > > > > Signed-off-by: Len Baker <len.baker@gmx.com> > > ... > > > diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c > > index f6d462d0be2d..7aea6c502316 100644 > > --- a/drivers/edac/edac_mc.c > > +++ b/drivers/edac/edac_mc.c > > @@ -1032,6 +1032,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type, > > int i, n_labels = 0; > > struct edac_raw_error_desc *e = &mci->error_desc; > > bool any_memory = true; > > + size_t len; > > > > edac_dbg(3, "MC%d\n", mci->mc_idx); > > > > @@ -1086,6 +1087,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type, > > */ > > p = e->label; > > *p = '\0'; > > + len = sizeof(e->label); > > > > mci_for_each_dimm(mci, dimm) { > > if (top_layer >= 0 && top_layer != dimm->location[0]) > > @@ -1114,10 +1116,12 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type, > > *p = '\0'; > > } else { > > if (p != e->label) { > > - strcpy(p, OTHER_LABEL); > > - p += strlen(OTHER_LABEL); > > + strscpy(p, OTHER_LABEL, len); > > Hm, maybe I'm missing something but looking at that strscpy() > definition, why aren't you doing: > > num = strscpy(p, OTHER_LABEL, len); > if (num < 0) > /* just in case */ > break; > > len -= num; > p += num; > > since that function supposedly returns the number of chars copied.
Yes, you are right. The same discussion happened in the v3 review [2] and I agree with the reasons that Robert Richter exposed. Using the strlen() implementation it is not necessary to check the return code of strcpy and we can assume a silent truncation.
[2] https://lore.kernel.org/linux-hardening/YRN+8u59lJ6MWsOL@rric.localdomain/
Regards, Len
> > + len -= strlen(p); > > + p += strlen(p); > > } > > - strcpy(p, dimm->label); > > + strscpy(p, dimm->label, len); > > + len -= strlen(p); > > p += strlen(p); > > Ditto. > > Thx. > > -- > Regards/Gruss, > Boris. > > https://people.kernel.org/tglx/notes-about-netiquette
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