| Message ID | 20231011-strncpy-drivers-net-ethernet-qlogic-qed-qed_debug-c-v1-1-60c9ca2d54a2@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | qed: replace uses of strncpy | expand |
On Wed, Oct 11, 2023 at 10:20:10PM +0000, Justin Stitt wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > This patch eliminates three uses of strncpy(): > > Firstly, `dest` is expected to be NUL-terminated which is evident by the > manual setting of a NUL-byte at size - 1. For this use specifically, > strscpy() is a viable replacement due to the fact that it guarantees > NUL-termination on the destination buffer. > > The next two changes utilizes snprintf() to make the copying behavior > more obvious. Previously, strncpy() was used to overwrite the first 3 > characters of mem_name and type_name by setting a length argument less > than the size of the buffers themselves. This enables, in a roundabout > way, creating a string like "ASD_BIG_RAM" or "ASD_RAM". Let's just use > snprintf() with a precision specifier to hold the name prefix to exactly > 3 characters long. > > To be clear, there are no buffer overread bugs in the current code as > the sizes and offsets are carefully managed such that buffers are > NUL-terminated. However, with these changes, the code is now more robust > and less ambiguous (and hopefully easier to read). > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@vger.kernel.org > Cc: Kees Cook <keescook@chromium.org> > Signed-off-by: Justin Stitt <justinstitt@google.com> > --- > Note: build-tested only. > > Found with: $ rg "strncpy\(" > --- > drivers/net/ethernet/qlogic/qed/qed_debug.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/drivers/net/ethernet/qlogic/qed/qed_debug.c b/drivers/net/ethernet/qlogic/qed/qed_debug.c > index cdcead614e9f..0a4fd1b04353 100644 > --- a/drivers/net/ethernet/qlogic/qed/qed_debug.c > +++ b/drivers/net/ethernet/qlogic/qed/qed_debug.c > @@ -3192,8 +3192,8 @@ static u32 qed_grc_dump_big_ram(struct qed_hwfn *p_hwfn, > { > struct dbg_tools_data *dev_data = &p_hwfn->dbg_info; > u32 block_size, ram_size, offset = 0, reg_val, i; > - char mem_name[12] = "???_BIG_RAM"; > - char type_name[8] = "???_RAM"; > + char mem_name[12]; > + char type_name[8]; > struct big_ram_defs *big_ram; > > big_ram = &s_big_ram_defs[big_ram_id]; > @@ -3204,8 +3204,11 @@ static u32 qed_grc_dump_big_ram(struct qed_hwfn *p_hwfn, > BIT(big_ram->is_256b_bit_offset[dev_data->chip_id]) ? 256 > : 128; > > - strncpy(type_name, big_ram->instance_name, BIG_RAM_NAME_LEN); > - strncpy(mem_name, big_ram->instance_name, BIG_RAM_NAME_LEN); > + snprintf(mem_name, sizeof(mem_name), "%.*s_BIG_RAM", > + BIG_RAM_NAME_LEN, big_ram->instance_name); > + > + snprintf(type_name, sizeof(type_name), "%.*s_RAM", > + BIG_RAM_NAME_LEN, big_ram->instance_name); I actually think just replacing strncpy with memcpy makes more sense and is what this code intended. It already assumes big_ram->instance_name is always 3 characters (which it is): static struct big_ram_defs s_big_ram_defs[] = { {"BRB", MEM_GROUP_BRB_MEM, MEM_GROUP_BRB_RAM, ... {"BTB", MEM_GROUP_BTB_MEM, MEM_GROUP_BTB_RAM, ... {"BMB", MEM_GROUP_BMB_MEM, MEM_GROUP_BMB_RAM, ... So just copy those three bytes -- no need to call into sprintf for it. > > /* Dump memory header */ > offset += qed_grc_dump_mem_hdr(p_hwfn, > @@ -6359,8 +6362,7 @@ static void qed_read_str_from_buf(void *buf, u32 *offset, u32 size, char *dest) > { > const char *source_str = &((const char *)buf)[*offset]; > > - strncpy(dest, source_str, size); > - dest[size - 1] = '\0'; > + strscpy(dest, source_str, size); > *offset += size; > } This one looks right to me.
diff --git a/drivers/net/ethernet/qlogic/qed/qed_debug.c b/drivers/net/ethernet/qlogic/qed/qed_debug.c index cdcead614e9f..0a4fd1b04353 100644 --- a/drivers/net/ethernet/qlogic/qed/qed_debug.c +++ b/drivers/net/ethernet/qlogic/qed/qed_debug.c @@ -3192,8 +3192,8 @@ static u32 qed_grc_dump_big_ram(struct qed_hwfn *p_hwfn, { struct dbg_tools_data *dev_data = &p_hwfn->dbg_info; u32 block_size, ram_size, offset = 0, reg_val, i; - char mem_name[12] = "???_BIG_RAM"; - char type_name[8] = "???_RAM"; + char mem_name[12]; + char type_name[8]; struct big_ram_defs *big_ram; big_ram = &s_big_ram_defs[big_ram_id]; @@ -3204,8 +3204,11 @@ static u32 qed_grc_dump_big_ram(struct qed_hwfn *p_hwfn, BIT(big_ram->is_256b_bit_offset[dev_data->chip_id]) ? 256 : 128; - strncpy(type_name, big_ram->instance_name, BIG_RAM_NAME_LEN); - strncpy(mem_name, big_ram->instance_name, BIG_RAM_NAME_LEN); + snprintf(mem_name, sizeof(mem_name), "%.*s_BIG_RAM", + BIG_RAM_NAME_LEN, big_ram->instance_name); + + snprintf(type_name, sizeof(type_name), "%.*s_RAM", + BIG_RAM_NAME_LEN, big_ram->instance_name); /* Dump memory header */ offset += qed_grc_dump_mem_hdr(p_hwfn, @@ -6359,8 +6362,7 @@ static void qed_read_str_from_buf(void *buf, u32 *offset, u32 size, char *dest) { const char *source_str = &((const char *)buf)[*offset]; - strncpy(dest, source_str, size); - dest[size - 1] = '\0'; + strscpy(dest, source_str, size); *offset += size; }
strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. This patch eliminates three uses of strncpy(): Firstly, `dest` is expected to be NUL-terminated which is evident by the manual setting of a NUL-byte at size - 1. For this use specifically, strscpy() is a viable replacement due to the fact that it guarantees NUL-termination on the destination buffer. The next two changes utilizes snprintf() to make the copying behavior more obvious. Previously, strncpy() was used to overwrite the first 3 characters of mem_name and type_name by setting a length argument less than the size of the buffers themselves. This enables, in a roundabout way, creating a string like "ASD_BIG_RAM" or "ASD_RAM". Let's just use snprintf() with a precision specifier to hold the name prefix to exactly 3 characters long. To be clear, there are no buffer overread bugs in the current code as the sizes and offsets are carefully managed such that buffers are NUL-terminated. However, with these changes, the code is now more robust and less ambiguous (and hopefully easier to read). Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@vger.kernel.org Cc: Kees Cook <keescook@chromium.org> Signed-off-by: Justin Stitt <justinstitt@google.com> --- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/net/ethernet/qlogic/qed/qed_debug.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2 change-id: 20231011-strncpy-drivers-net-ethernet-qlogic-qed-qed_debug-c-211d594201e4 Best regards, -- Justin Stitt <justinstitt@google.com>