| Message ID | 20210829161547.6069-1-len.baker@gmx.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v5] EDAC/mc: Prefer strscpy or scnprintf over strcpy | expand |
On Sun, 2021-08-29 at 18:15 +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() [1]. > > However, to simplify and clarify the code, to concatenate labels use > the scnprintf() function. This way it is not necessary to check the > return value of strscpy (-E2BIG if the parameter count is 0 or the src > was truncated) since the scnprintf returns always the number of chars > written into the buffer. This function returns always a nul-terminated > string even if it needs to be truncated. [] > diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c [] > @@ -1113,12 +1116,11 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type, > p = e->label; > *p = '\0'; > } else { > - if (p != e->label) { > - strcpy(p, OTHER_LABEL); > - p += strlen(OTHER_LABEL); > - } > - strcpy(p, dimm->label); > - p += strlen(p); > + const char *or = (p != e->label) ? OTHER_LABEL : ""; > + > + n = scnprintf(p, len, "%s%s", or, dimm->label); > + len -= n; > + p += n; A very common and intelligible mechanism for this is: const char *prefix = ""; int n = 0; ... n += scnprintf(e->label + n, sizeof(e->label) - n, "%s%s", prefix, dimm->label); prefix = " or ";
Hi, On Sun, Aug 29, 2021 at 09:38:37AM -0700, Joe Perches wrote: > On Sun, 2021-08-29 at 18:15 +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() [1]. > > > > However, to simplify and clarify the code, to concatenate labels use > > the scnprintf() function. This way it is not necessary to check the > > return value of strscpy (-E2BIG if the parameter count is 0 or the src > > was truncated) since the scnprintf returns always the number of chars > > written into the buffer. This function returns always a nul-terminated > > string even if it needs to be truncated. > [] > > diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c > [] > > @@ -1113,12 +1116,11 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type, > > p = e->label; > > *p = '\0'; > > } else { > > - if (p != e->label) { > > - strcpy(p, OTHER_LABEL); > > - p += strlen(OTHER_LABEL); > > - } > > - strcpy(p, dimm->label); > > - p += strlen(p); > > + const char *or = (p != e->label) ? OTHER_LABEL : ""; > > + > > + n = scnprintf(p, len, "%s%s", or, dimm->label); > > + len -= n; > > + p += n; > > A very common and intelligible mechanism for this is: > > const char *prefix = ""; > int n = 0; > ... > n += scnprintf(e->label + n, sizeof(e->label) - n, > "%s%s", prefix, dimm->label); > prefix = " or "; > Ok, I will send a new version using this common mechanism. Thanks for the advise. Regards, Len
diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c index f6d462d0be2d..4fe1286ad7a2 100644 --- a/drivers/edac/edac_mc.c +++ b/drivers/edac/edac_mc.c @@ -1032,6 +1032,8 @@ 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; + int n; edac_dbg(3, "MC%d\n", mci->mc_idx); @@ -1086,6 +1088,7 @@ 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]) @@ -1113,12 +1116,11 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type, p = e->label; *p = '\0'; } else { - if (p != e->label) { - strcpy(p, OTHER_LABEL); - p += strlen(OTHER_LABEL); - } - strcpy(p, dimm->label); - p += strlen(p); + const char *or = (p != e->label) ? OTHER_LABEL : ""; + + n = scnprintf(p, len, "%s%s", or, dimm->label); + len -= n; + p += n; } /* @@ -1140,9 +1142,9 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type, } if (any_memory) - strcpy(e->label, "any memory"); + strscpy(e->label, "any memory", sizeof(e->label)); else if (!*e->label) - strcpy(e->label, "unknown memory"); + strscpy(e->label, "unknown memory", sizeof(e->label)); edac_inc_csrow(e, row, chan);
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() [1]. However, to simplify and clarify the code, to concatenate labels use the scnprintf() function. This way it is not necessary to check the return value of strscpy (-E2BIG if the parameter count is 0 or the src was truncated) since the scnprintf returns always the number of chars written into the buffer. This function returns always a nul-terminated string even if it needs to be truncated. The main reason behind this patch is to remove all the strcpy() uses from the kernel with the purpose to clean up the proliferation of str*cpy() functions. Later on, the next step will be remove all the strcpy implementations [2]. [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy [2] https://github.com/KSPP/linux/issues/88 Signed-off-by: Len Baker <len.baker@gmx.com> --- Hi, Next try. I hope this version will be accepted. Anyway, thanks for the reviews and patience ;) Thanks, Len Changelog v1 -> v2 - Use the strscpy() instead of scnprintf() to add labels and follow a code pattern more similar to the current one (advance "p" and decrement "left") (Robert Richter). Changelog v2 -> v3 - Rename the "left" variable to "len" (Robert Richter). - Use strlen(p) instead of strlen(OTHER_LABEL) to decrement "len" and increment "p" as otherwise "left" could underflow and p overflow (Robert Richter). Changelog v3 -> v4 - Change the commit subject (Joe Perches). - Fix broken logic (Robert Richter). - Rebase against v5.14-rc5. Changelog v4 -> v5 - Change the commit subject. - Clarify why the change is being made by adding more info to the commit message (Borislav Petkov). - Use scnprintf instead of strscpy (Joe Perches). - Rebase against v5.14-rc7. Previous versions: v1 https://lore.kernel.org/linux-hardening/20210725162954.9861-1-len.baker@gmx.com/ v2 https://lore.kernel.org/linux-hardening/20210801143558.12674-1-len.baker@gmx.com/ v3 https://lore.kernel.org/linux-hardening/20210807155957.10069-1-len.baker@gmx.com/ v4 https://lore.kernel.org/linux-hardening/20210814075527.5999-1-len.baker@gmx.com/ drivers/edac/edac_mc.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) -- 2.25.1