[net,1/2] ipvs: Fix clamp() of ip_vs_conn_tab on small memory systems

Commit Message

Pablo Neira Ayuso Dec. 18, 2024, 11:41 p.m. UTC

From: David Laight <[e-mail]>

The 'max_avail' value is calculated from the system memory
size using order_base_2().
order_base_2(x) is defined as '(x) ? fn(x) : 0'.
The compiler generates two copies of the code that follows
and then expands clamp(max, min, PAGE_SHIFT - 12) (11 on 32bit).
This triggers a compile-time assert since min is 5.

In reality a system would have to have less than 512MB memory
for the bounds passed to clamp to be reversed.

Swap the order of the arguments to clamp() to avoid the warning.

Replace the clamp_val() on the line below with clamp().
clamp_val() is just 'an accident waiting to happen' and not needed here.

Detected by compile time checks added to clamp(), specifically:
minmax.h: use BUILD_BUG_ON_MSG() for the lo < hi test in clamp()

Reported-by: Linux Kernel Functional Testing <[e-mail]>
Closes: https://lore.kernel.org/all/[e-mail]/
Fixes: 4f325e26277b ("ipvs: dynamically limit the connection hash table")
Tested-by: Bartosz Golaszewski <[e-mail]>
Reviewed-by: Bartosz Golaszewski <[e-mail]>
Signed-off-by: David Laight <[e-mail]>
Acked-by: Julian Anastasov <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>
---
 net/netfilter/ipvs/ip_vs_conn.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

[e-mail] Dec. 19, 2024, 9:10 a.m. UTC | #1

Hello:

This series was applied to netdev/net.git (main)
by Pablo Neira Ayuso <[e-mail]>:

On Thu, 19 Dec 2024 00:41:36 +0100 you wrote:
> From: David Laight <[e-mail]>
> 
> The 'max_avail' value is calculated from the system memory
> size using order_base_2().
> order_base_2(x) is defined as '(x) ? fn(x) : 0'.
> The compiler generates two copies of the code that follows
> and then expands clamp(max, min, PAGE_SHIFT - 12) (11 on 32bit).
> This triggers a compile-time assert since min is 5.
> 
> [...]

Here is the summary with links:
  - [net,1/2] ipvs: Fix clamp() of ip_vs_conn_tab on small memory systems
    https://git.kernel.org/netdev/net/c/cf2c97423a4f
  - [net,2/2] netfilter: ipset: Fix for recursive locking warning
    https://git.kernel.org/netdev/net/c/70b6f46a4ed8

You are awesome, thank you!

Patch

diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c
index 98d7dbe3d787..c0289f83f96d 100644
--- a/net/netfilter/ipvs/ip_vs_conn.c
+++ b/net/netfilter/ipvs/ip_vs_conn.c
@@ -1495,8 +1495,8 @@  int __init ip_vs_conn_init(void)
 	max_avail -= 2;		/* ~4 in hash row */
 	max_avail -= 1;		/* IPVS up to 1/2 of mem */
 	max_avail -= order_base_2(sizeof(struct ip_vs_conn));
-	max = clamp(max, min, max_avail);
-	ip_vs_conn_tab_bits = clamp_val(ip_vs_conn_tab_bits, min, max);
+	max = clamp(max_avail, min, max);
+	ip_vs_conn_tab_bits = clamp(ip_vs_conn_tab_bits, min, max);
 	ip_vs_conn_tab_size = 1 << ip_vs_conn_tab_bits;
 	ip_vs_conn_tab_mask = ip_vs_conn_tab_size - 1;