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Message-ID: <9477fcb5-1cca-435e-a1af-e02edff1551c@embeddedor.com> Date: Mon, 9 Oct 2023 09:03:08 -0600 From: "Gustavo A. R. Silva" <gustavo@...eddedor.com> To: Jason Andryuk <jandryuk@...il.com>, Kees Cook <keescook@...omium.org> Cc: Christian Lamparter <chunkeey@...glemail.com>, Kalle Valo <kvalo@...nel.org>, "Gustavo A. R. Silva" <gustavoars@...nel.org>, linux-wireless@...r.kernel.org, linux-hardening@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org, llvm@...ts.linux.dev Subject: Re: [PATCH] wifi: p54: Annotate struct p54_cal_database with __counted_by On 10/9/23 16:55, Jason Andryuk wrote: > Hi, > > I randomly peeked at this patch. Unfortunately, I am not familiar > with the actual p54 code. > > On Fri, Oct 6, 2023 at 4:17 PM Kees Cook <keescook@...omium.org> wrote: >> >> Prepare for the coming implementation by GCC and Clang of the __counted_by >> attribute. Flexible array members annotated with __counted_by can have >> their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for >> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family >> functions). >> >> As found with Coccinelle[1], add __counted_by for struct p54_cal_database. >> >> Cc: Christian Lamparter <chunkeey@...glemail.com> >> Cc: Kalle Valo <kvalo@...nel.org> >> Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org> >> Cc: linux-wireless@...r.kernel.org >> Cc: linux-hardening@...r.kernel.org >> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1] >> Signed-off-by: Kees Cook <keescook@...omium.org> >> --- >> drivers/net/wireless/intersil/p54/p54.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/net/wireless/intersil/p54/p54.h b/drivers/net/wireless/intersil/p54/p54.h >> index 3356ea708d81..770e348d1f6c 100644 >> --- a/drivers/net/wireless/intersil/p54/p54.h >> +++ b/drivers/net/wireless/intersil/p54/p54.h >> @@ -126,7 +126,7 @@ struct p54_cal_database { >> size_t entry_size; >> size_t offset; >> size_t len; >> - u8 data[]; >> + u8 data[] __counted_by(entries); > > This looks incorrect - I think you want __counted_by(len)? The I think you're right. More comments below... > presence of entry_size made me suspicious. > >> }; > > This is the function that creates struct p54_cal_database: > > static struct p54_cal_database *p54_convert_db(struct pda_custom_wrapper *src, > size_t total_len) > { > struct p54_cal_database *dst; > size_t payload_len, entries, entry_size, offset; > > payload_len = le16_to_cpu(src->len); > entries = le16_to_cpu(src->entries); > entry_size = le16_to_cpu(src->entry_size); > offset = le16_to_cpu(src->offset); > if (((entries * entry_size + offset) != payload_len) || > (payload_len + sizeof(*src) != total_len)) > return NULL; > > dst = kmalloc(sizeof(*dst) + payload_len, GFP_KERNEL); > if (!dst) > return NULL; > > dst->entries = entries; > dst->entry_size = entry_size; > dst->offset = offset; > dst->len = payload_len; > > memcpy(dst->data, src->data, payload_len); > return dst; > } > > You can see that kmalloc is performed with `sizeof(*dst) + > payload_len`, and payload_len is assigned to ->len. This should be changed to: - dst = kmalloc(sizeof(*dst) + payload_len, GFP_KERNEL); + dst = kmalloc(struct_size(dst, data, payload_len), GFP_KERNEL); > > I don't read Coccinelle, but, if this patch was auto-generated, I > wonder if the script has an error. With the struct_size() change, the Coccinelle script should be able to generate a correct patch for this. -- Gustavo
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