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xfrm: xfrm_alloc_spi shouldn't use 0 as SPI

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x->id.spi == 0 means "no SPI assigned", but since commit
94f39804d8 ("xfrm: Duplicate SPI Handling"), we now create states
and add them to the byspi list with this value.

__xfrm_state_delete doesn't remove those states from the byspi list,
since they shouldn't be there, and this shows up as a UAF the next
time we go through the byspi list.

Reported-by: syzbot+a25ee9d20d31e483ba7b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=a25ee9d20d31e483ba7b
Fixes: 94f39804d8 ("xfrm: Duplicate SPI Handling")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Sabrina Dubroca 2025-08-29 10:54:15 +02:00 • committed by Steffen Klassert
parent 52565a9352
commit cd8ae32e4e
1 changed files with 3 additions and 0 deletions
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3
net/xfrm/xfrm_state.c
View file

@ -2583,6 +2583,8 @@ int xfrm_alloc_spi(struct xfrm_state *x, u32 low, u32 high,
for (h = 0; h < range; h++) {
u32 spi = (low == high) ? low : get_random_u32_inclusive(low, high);
if (spi == 0)
goto next;
newspi = htonl(spi);
spin_lock_bh(&net->xfrm.xfrm_state_lock);
@ -2598,6 +2600,7 @@ int xfrm_alloc_spi(struct xfrm_state *x, u32 low, u32 high,
xfrm_state_put(x0);
spin_unlock_bh(&net->xfrm.xfrm_state_lock);
next:
if (signal_pending(current)) {
err = -ERESTARTSYS;
goto unlock;