From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Behun Date: Tue, 16 Mar 2021 15:15:27 +0100 Subject: [PATCH u-boot v3 01/39] regmap: fix a serious pointer casting bug In-Reply-To: <20210316135844.7fb3czkwqdkadmze@ti.com> References: <20210316122609.6523-1-marek.behun@nic.cz> <20210316122609.6523-2-marek.behun@nic.cz> <20210316135844.7fb3czkwqdkadmze@ti.com> Message-ID: <20210316151528.7bd8ade5@nic.cz> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Tue, 16 Mar 2021 19:28:46 +0530 Pratyush Yadav wrote: > On 16/03/21 01:25PM, Marek Beh?n wrote: > > There is a serious bug in regmap_read() and regmap_write() functions > > where an uint pointer is cast to (void *) which is then cast to (u8 *), > > (u16 *), (u32 *) or (u64 *), depending on register width of the map. > > > > For example given a regmap with 16-bit register width the code > > int val = 0x12340000; > > regmap_read(map, 0, &val); > > only changes the lower 16 bits of val on little-endian machines. > > The upper 16 bits will remain 0x1234. > > > > Nobody noticed this probably because this bug can be triggered with > > regmap_write() only on big-endian architectures (which are not used by > > many people anymore), and on little endian this bug has consequences > > only if register width is 8 or 16 bits and also the memory place to > > which regmap_read() should store it's result has non-zero upper bits, > > which it seems doesn't happen anywhere in U-Boot normally. CI managed to > > trigger this bug in unit test of dm_test_devm_regmap_field when compiled > > for sandbox_defconfig using LTO. > > > > Fix this simply by taking into account that regmap_raw_read() and > > regmap_raw_write() behave as if the data given to these functions were > > in little-endian format, i.e. use cpu_to_le32() / le32_to_cpu(). In > > regmap_read() also zero out the space so that we don't get invalid > > result if regmap_raw_read() does not fill the whole object. > > > > Signed-off-by: Marek Beh?n > > Reviewed-by: Simon Glass > > Reviewed-by: Heiko Schocher > > Reviewed-by: Bin Meng > > --- > > drivers/core/regmap.c | 13 ++++++++++++- > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/core/regmap.c b/drivers/core/regmap.c > > index b51ce108c1..5d37006fff 100644 > > --- a/drivers/core/regmap.c > > +++ b/drivers/core/regmap.c > > @@ -435,7 +435,16 @@ int regmap_raw_read(struct regmap *map, uint offset, void *valp, size_t val_len) > > > > int regmap_read(struct regmap *map, uint offset, uint *valp) > > { > > - return regmap_raw_read(map, offset, valp, map->width); > > + int res; > > + > > + *valp = 0; > > + res = regmap_raw_read(map, offset, valp, map->width); > > + if (res) > > + return res; > > + > > + *valp = le32_to_cpu(*valp); > > Looks like I'm a bit late to the party and Simon has already applied > this patch. Where did he apply? I don't see it applied in u-boot-dm. > Anyway, I don't see why this is correct. regmap_raw_read() > calls regmap_raw_read_range(), which calls the helpers __read_16(), > __read_32() and so on. > > Take __read_16() for example. It takes the regmap's endianness and then > based on that calls in_le16() or in_be16(). These calls translate to > le16_to_cpu(__raw_readw(a)) or be16_to_cpu(__raw_readw(a)). Or the > regmap is native endian in which case it is a simple readw(a). > > In all 3 cases the value returned is in cpu endianness. But you claim > that "regmap_raw_read() and regmap_raw_write() behave as if the data > given to these functions were in little-endian format". > > This is fine on a little endian cpu but on a big endian cpu you would > reverse the byte order, no? Same for writes. I made a mistake. Somehow I thought that le32_to_cpu() will fix this, because it will move the read bytes into the correct position. But somehow I forgot that it will also reverse the byte order /o\ :D I shall fix this and send a new version :D