From 1cfb5e57886aa69a992ff0ebd32e4651eb0fc995 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 15 Nov 2024 12:43:03 -0800 Subject: Revert "net: ethtool: Avoid thousands of -Wflex-array-member-not-at-end warnings" This reverts commit 3bd9b9abdf1563a22041b7255baea6d449902f1a. We cannot use the new tagged struct group because it throws C++ errors even under "extern C". Signed-off-by: Kees Cook Link: https://patch.msgid.link/20241115204308.3821419-1-kees@kernel.org Signed-off-by: Jakub Kicinski --- include/linux/ethtool.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h index 299280c94d07..b8b935b52603 100644 --- a/include/linux/ethtool.h +++ b/include/linux/ethtool.h @@ -211,7 +211,7 @@ void ethtool_rxfh_context_lost(struct net_device *dev, u32 context_id); * fields, but they are allowed to overwrite them (will be ignored). */ struct ethtool_link_ksettings { - struct ethtool_link_settings_hdr base; + struct ethtool_link_settings base; struct { __ETHTOOL_DECLARE_LINK_MODE_MASK(supported); __ETHTOOL_DECLARE_LINK_MODE_MASK(advertising); -- cgit v1.2.3 From ebda123fe703f492d7d557a4da00888ddec4779e Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 15 Nov 2024 12:43:04 -0800 Subject: Revert "UAPI: ethtool: Use __struct_group() in struct ethtool_link_settings" This reverts commit 43d3487035e9a86fad952de4240a518614240d43. We cannot use tagged struct groups in UAPI because C++ will throw syntax errors even under "extern C". Signed-off-by: Kees Cook Link: https://patch.msgid.link/20241115204308.3821419-2-kees@kernel.org Signed-off-by: Jakub Kicinski --- include/uapi/linux/ethtool.h | 33 +++++++++++++++------------------ 1 file changed, 15 insertions(+), 18 deletions(-) (limited to 'include') diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h index fc1f54b065f9..c405ed63acfa 100644 --- a/include/uapi/linux/ethtool.h +++ b/include/uapi/linux/ethtool.h @@ -2511,24 +2511,21 @@ enum ethtool_reset_flags { * autonegotiation; 0 if unknown or not applicable. Read-only. */ struct ethtool_link_settings { - /* New members MUST be added within the __struct_group() macro below. */ - __struct_group(ethtool_link_settings_hdr, hdr, /* no attrs */, - __u32 cmd; - __u32 speed; - __u8 duplex; - __u8 port; - __u8 phy_address; - __u8 autoneg; - __u8 mdio_support; - __u8 eth_tp_mdix; - __u8 eth_tp_mdix_ctrl; - __s8 link_mode_masks_nwords; - __u8 transceiver; - __u8 master_slave_cfg; - __u8 master_slave_state; - __u8 rate_matching; - __u32 reserved[7]; - ); + __u32 cmd; + __u32 speed; + __u8 duplex; + __u8 port; + __u8 phy_address; + __u8 autoneg; + __u8 mdio_support; + __u8 eth_tp_mdix; + __u8 eth_tp_mdix_ctrl; + __s8 link_mode_masks_nwords; + __u8 transceiver; + __u8 master_slave_cfg; + __u8 master_slave_state; + __u8 rate_matching; + __u32 reserved[7]; __u32 link_mode_masks[]; /* layout of link_mode_masks fields: * __u32 map_supported[link_mode_masks_nwords]; -- cgit v1.2.3 From 96c677fca54a28fcfea4dbab9c1f2530bd0a08d1 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 15 Nov 2024 12:43:05 -0800 Subject: UAPI: ethtool: Avoid flex-array in struct ethtool_link_settings struct ethtool_link_settings tends to be used as a header for other structures that have trailing bytes[1], but has a trailing flexible array itself. Using this overlapped with other structures leads to ambiguous object sizing in the compiler, so we want to avoid such situations (which have caused real bugs in the past). Detecting this can be done with -Wflex-array-member-not-at-end, which will need to be enabled globally. Using a tagged struct_group() to create a new ethtool_link_settings_hdr structure isn't possible as it seems we cannot use the tagged variant of struct_group() due to syntax issues from C++'s perspective (even within "extern C")[2]. Instead, we can just leave the offending member defined in UAPI and remove it from the kernel's view of the structure, as Linux doesn't actually use this member at all. There is also no change in size since it was already a flexible array that didn't contribute to size returned by any use of sizeof(). Reported-by: Jakub Kicinski Closes: https://lore.kernel.org/lkml/20241109100213.262a2fa0@kernel.org/ [2] Link: https://lore.kernel.org/lkml/0bc2809fe2a6c11dd4c8a9a10d9bd65cccdb559b.1730238285.git.gustavoars@kernel.org/ [1] Signed-off-by: Kees Cook Reviewed-by: Jakub Kicinski Link: https://patch.msgid.link/20241115204308.3821419-3-kees@kernel.org Signed-off-by: Jakub Kicinski --- include/uapi/linux/ethtool.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include') diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h index c405ed63acfa..7e1b3820f91f 100644 --- a/include/uapi/linux/ethtool.h +++ b/include/uapi/linux/ethtool.h @@ -2526,12 +2526,19 @@ struct ethtool_link_settings { __u8 master_slave_state; __u8 rate_matching; __u32 reserved[7]; +#ifndef __KERNEL__ + /* Linux builds with -Wflex-array-member-not-at-end but does + * not use the "link_mode_masks" member. Leave it defined for + * userspace for now, and when userspace wants to start using + * -Wfamnae, we'll need a new solution. + */ __u32 link_mode_masks[]; /* layout of link_mode_masks fields: * __u32 map_supported[link_mode_masks_nwords]; * __u32 map_advertising[link_mode_masks_nwords]; * __u32 map_lp_advertising[link_mode_masks_nwords]; */ +#endif }; /** -- cgit v1.2.3