* Re: [syzbot] [mm?] WARNING in try_grab_page
2023-07-25 8:36 ` [syzbot] [mm?] WARNING in try_grab_page Sven Schnelle
@ 2023-07-25 9:28 ` David Howells
2023-07-26 8:25 ` David Howells
2023-07-26 8:31 ` David Howells
2 siblings, 0 replies; 6+ messages in thread
From: David Howells @ 2023-07-25 9:28 UTC (permalink / raw)
To: Sven Schnelle
Cc: dhowells, syzbot, akpm, linux-kernel, linux-mm, syzkaller-bugs,
Herbert Xu, David S. Miller, linux-crypto
Sven Schnelle <svens@linux.ibm.com> wrote:
>
> I looked into this issue. What syzkaller is doing is opening an AF_ALG
> socket, and sending a large message which will eventually end in -EFAULT.
> Looking at the code in crypto/algif_hash.c i see that hash_sendmsg is
> calling extract_iter_to_sg() -> extract_user_to_sg(). In the -EFAULT
> case, this function is calling put_page(), which looks like a leftover
> from the old pinning interface. I think this should be a
> unpin_user_page() call now.
>
> However, hash_sendmsg() also unpins via af_alg_free_sg() in the error
> path. From an API perspective, i would prefer if extract_user_to_sg()
> does the unpinning on error. Any thoughts?
Good catch, thanks. I'll whip up a patch or two for it.
David
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] [mm?] WARNING in try_grab_page
2023-07-25 8:36 ` [syzbot] [mm?] WARNING in try_grab_page Sven Schnelle
2023-07-25 9:28 ` David Howells
@ 2023-07-26 8:25 ` David Howells
2023-07-26 8:31 ` David Howells
2 siblings, 0 replies; 6+ messages in thread
From: David Howells @ 2023-07-26 8:25 UTC (permalink / raw)
To: Sven Schnelle
Cc: dhowells, syzbot, akpm, linux-kernel, linux-mm, syzkaller-bugs,
Herbert Xu, David S. Miller, linux-crypto
Sven Schnelle <svens@linux.ibm.com> wrote:
> However, hash_sendmsg() also unpins via af_alg_free_sg() in the error
> path. From an API perspective, i would prefer if extract_user_to_sg()
> does the unpinning on error. Any thoughts?
In the event of an error, extract_user_to_sg() unpins only the pages it added
to the scatterlist; it doesn't unpin any pages that were already there and
doesn't free the scatterlist; it also decrements sgtable->nents so that the
caller doesn't see the pages it attempted to add, so calling af_alg_free_sg()
shouldn't hurt.
Note that the error path also frees the result, so we do need to do at least
part of it.
David
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [syzbot] [mm?] WARNING in try_grab_page
2023-07-25 8:36 ` [syzbot] [mm?] WARNING in try_grab_page Sven Schnelle
2023-07-25 9:28 ` David Howells
2023-07-26 8:25 ` David Howells
@ 2023-07-26 8:31 ` David Howells
2023-07-26 8:31 ` syzbot
2 siblings, 1 reply; 6+ messages in thread
From: David Howells @ 2023-07-26 8:31 UTC (permalink / raw)
To: syzbot
Cc: dhowells, Sven Schnelle, akpm, linux-kernel, linux-mm,
syzkaller-bugs, Herbert Xu, David S. Miller, linux-crypto
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
lib/scatterlist: Fix error handling in extract_iter_to_sg()
Fix the error handling in extract_iter_to_sg(). Pages need to be unpinned,
not put, and only if they actually got pinned (which is the case in
extract_user_to_sg()).
The bug may result in a warning like the following:
WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 __lse_atomic_add arch/arm64/include/asm/atomic_lse.h:27 [inline]
WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 arch_atomic_add arch/arm64/include/asm/atomic.h:28 [inline]
WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 raw_atomic_add include/linux/atomic/atomic-arch-fallback.h:537 [inline]
WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 atomic_add include/linux/atomic/atomic-instrumented.h:105 [inline]
WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 try_grab_page+0x108/0x160 mm/gup.c:252
...
pc : try_grab_page+0x108/0x160 mm/gup.c:229
lr : follow_page_pte+0x174/0x3e4 mm/gup.c:651
...
Call trace:
__lse_atomic_add arch/arm64/include/asm/atomic_lse.h:27 [inline]
arch_atomic_add arch/arm64/include/asm/atomic.h:28 [inline]
raw_atomic_add include/linux/atomic/atomic-arch-fallback.h:537 [inline]
atomic_add include/linux/atomic/atomic-instrumented.h:105 [inline]
try_grab_page+0x108/0x160 mm/gup.c:252
follow_pmd_mask mm/gup.c:734 [inline]
follow_pud_mask mm/gup.c:765 [inline]
follow_p4d_mask mm/gup.c:782 [inline]
follow_page_mask+0x12c/0x2e4 mm/gup.c:839
__get_user_pages+0x174/0x30c mm/gup.c:1217
__get_user_pages_locked mm/gup.c:1448 [inline]
__gup_longterm_locked+0x94/0x8f4 mm/gup.c:2142
internal_get_user_pages_fast+0x970/0xb60 mm/gup.c:3140
pin_user_pages_fast+0x4c/0x60 mm/gup.c:3246
iov_iter_extract_user_pages lib/iov_iter.c:1768 [inline]
iov_iter_extract_pages+0xc8/0x54c lib/iov_iter.c:1831
extract_user_to_sg lib/scatterlist.c:1123 [inline]
extract_iter_to_sg lib/scatterlist.c:1349 [inline]
extract_iter_to_sg+0x26c/0x6fc lib/scatterlist.c:1339
hash_sendmsg+0xc0/0x43c crypto/algif_hash.c:117
sock_sendmsg_nosec net/socket.c:725 [inline]
sock_sendmsg+0x54/0x60 net/socket.c:748
____sys_sendmsg+0x270/0x2ac net/socket.c:2494
___sys_sendmsg+0x80/0xdc net/socket.c:2548
__sys_sendmsg+0x68/0xc4 net/socket.c:2577
__do_sys_sendmsg net/socket.c:2586 [inline]
__se_sys_sendmsg net/socket.c:2584 [inline]
__arm64_sys_sendmsg+0x24/0x30 net/socket.c:2584
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x48/0x114 arch/arm64/kernel/syscall.c:52
el0_svc_common.constprop.0+0x44/0xe4 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x38/0xa4 arch/arm64/kernel/syscall.c:191
el0_svc+0x2c/0xb0 arch/arm64/kernel/entry-common.c:647
el0t_64_sync_handler+0xc0/0xc4 arch/arm64/kernel/entry-common.c:665
el0t_64_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:591
Fixes: 018584697533 ("netfs: Add a function to extract an iterator into a scatterlist")
Reported-by: syzbot+9b82859567f2e50c123e@syzkaller.appspotmail.com
Link: https://lore.kernel.org/linux-mm/000000000000273d0105ff97bf56@google.com/
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Sven Schnelle <svens@linux.ibm.com>
cc: akpm@linux-foundation.org
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: "David S. Miller" <davem@davemloft.net>
cc: Jeff Layton <jlayton@kernel.org>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-mm@kvack.org
cc: linux-crypto@vger.kernel.org
cc: linux-cachefs@redhat.com
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: netdev@vger.kernel.org
---
lib/scatterlist.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index e86231a44c3d..c65566b4dc66 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -1148,7 +1148,7 @@ static ssize_t extract_user_to_sg(struct iov_iter *iter,
failed:
while (sgtable->nents > sgtable->orig_nents)
- put_page(sg_page(&sgtable->sgl[--sgtable->nents]));
+ unpin_user_page(sg_page(&sgtable->sgl[--sgtable->nents]));
return res;
}
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [syzbot] [mm?] WARNING in try_grab_page
2023-07-26 8:31 ` David Howells
@ 2023-07-26 8:31 ` syzbot
0 siblings, 0 replies; 6+ messages in thread
From: syzbot @ 2023-07-26 8:31 UTC (permalink / raw)
To: dhowells
Cc: akpm, davem, dhowells, herbert, linux-crypto, linux-kernel,
linux-mm, svens, syzkaller-bugs
> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
This crash does not have a reproducer. I cannot test it.
>
> lib/scatterlist: Fix error handling in extract_iter_to_sg()
>
> Fix the error handling in extract_iter_to_sg(). Pages need to be unpinned,
> not put, and only if they actually got pinned (which is the case in
> extract_user_to_sg()).
>
> The bug may result in a warning like the following:
>
> WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 __lse_atomic_add arch/arm64/include/asm/atomic_lse.h:27 [inline]
> WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 arch_atomic_add arch/arm64/include/asm/atomic.h:28 [inline]
> WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 raw_atomic_add include/linux/atomic/atomic-arch-fallback.h:537 [inline]
> WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 atomic_add include/linux/atomic/atomic-instrumented.h:105 [inline]
> WARNING: CPU: 1 PID: 20384 at mm/gup.c:229 try_grab_page+0x108/0x160 mm/gup.c:252
> ...
> pc : try_grab_page+0x108/0x160 mm/gup.c:229
> lr : follow_page_pte+0x174/0x3e4 mm/gup.c:651
> ...
> Call trace:
> __lse_atomic_add arch/arm64/include/asm/atomic_lse.h:27 [inline]
> arch_atomic_add arch/arm64/include/asm/atomic.h:28 [inline]
> raw_atomic_add include/linux/atomic/atomic-arch-fallback.h:537 [inline]
> atomic_add include/linux/atomic/atomic-instrumented.h:105 [inline]
> try_grab_page+0x108/0x160 mm/gup.c:252
> follow_pmd_mask mm/gup.c:734 [inline]
> follow_pud_mask mm/gup.c:765 [inline]
> follow_p4d_mask mm/gup.c:782 [inline]
> follow_page_mask+0x12c/0x2e4 mm/gup.c:839
> __get_user_pages+0x174/0x30c mm/gup.c:1217
> __get_user_pages_locked mm/gup.c:1448 [inline]
> __gup_longterm_locked+0x94/0x8f4 mm/gup.c:2142
> internal_get_user_pages_fast+0x970/0xb60 mm/gup.c:3140
> pin_user_pages_fast+0x4c/0x60 mm/gup.c:3246
> iov_iter_extract_user_pages lib/iov_iter.c:1768 [inline]
> iov_iter_extract_pages+0xc8/0x54c lib/iov_iter.c:1831
> extract_user_to_sg lib/scatterlist.c:1123 [inline]
> extract_iter_to_sg lib/scatterlist.c:1349 [inline]
> extract_iter_to_sg+0x26c/0x6fc lib/scatterlist.c:1339
> hash_sendmsg+0xc0/0x43c crypto/algif_hash.c:117
> sock_sendmsg_nosec net/socket.c:725 [inline]
> sock_sendmsg+0x54/0x60 net/socket.c:748
> ____sys_sendmsg+0x270/0x2ac net/socket.c:2494
> ___sys_sendmsg+0x80/0xdc net/socket.c:2548
> __sys_sendmsg+0x68/0xc4 net/socket.c:2577
> __do_sys_sendmsg net/socket.c:2586 [inline]
> __se_sys_sendmsg net/socket.c:2584 [inline]
> __arm64_sys_sendmsg+0x24/0x30 net/socket.c:2584
> __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
> invoke_syscall+0x48/0x114 arch/arm64/kernel/syscall.c:52
> el0_svc_common.constprop.0+0x44/0xe4 arch/arm64/kernel/syscall.c:142
> do_el0_svc+0x38/0xa4 arch/arm64/kernel/syscall.c:191
> el0_svc+0x2c/0xb0 arch/arm64/kernel/entry-common.c:647
> el0t_64_sync_handler+0xc0/0xc4 arch/arm64/kernel/entry-common.c:665
> el0t_64_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:591
>
> Fixes: 018584697533 ("netfs: Add a function to extract an iterator into a scatterlist")
> Reported-by: syzbot+9b82859567f2e50c123e@syzkaller.appspotmail.com
> Link: https://lore.kernel.org/linux-mm/000000000000273d0105ff97bf56@google.com/
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Sven Schnelle <svens@linux.ibm.com>
> cc: akpm@linux-foundation.org
> cc: Herbert Xu <herbert@gondor.apana.org.au>
> cc: "David S. Miller" <davem@davemloft.net>
> cc: Jeff Layton <jlayton@kernel.org>
> cc: Steve French <sfrench@samba.org>
> cc: Shyam Prasad N <nspmangalore@gmail.com>
> cc: Rohith Surabattula <rohiths.msft@gmail.com>
> cc: Jens Axboe <axboe@kernel.dk>
> cc: Herbert Xu <herbert@gondor.apana.org.au>
> cc: "David S. Miller" <davem@davemloft.net>
> cc: Eric Dumazet <edumazet@google.com>
> cc: Jakub Kicinski <kuba@kernel.org>
> cc: Paolo Abeni <pabeni@redhat.com>
> cc: Matthew Wilcox <willy@infradead.org>
> cc: linux-mm@kvack.org
> cc: linux-crypto@vger.kernel.org
> cc: linux-cachefs@redhat.com
> cc: linux-cifs@vger.kernel.org
> cc: linux-fsdevel@vger.kernel.org
> cc: netdev@vger.kernel.org
> ---
> lib/scatterlist.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/scatterlist.c b/lib/scatterlist.c
> index e86231a44c3d..c65566b4dc66 100644
> --- a/lib/scatterlist.c
> +++ b/lib/scatterlist.c
> @@ -1148,7 +1148,7 @@ static ssize_t extract_user_to_sg(struct iov_iter *iter,
>
> failed:
> while (sgtable->nents > sgtable->orig_nents)
> - put_page(sg_page(&sgtable->sgl[--sgtable->nents]));
> + unpin_user_page(sg_page(&sgtable->sgl[--sgtable->nents]));
> return res;
> }
>
^ permalink raw reply [flat|nested] 6+ messages in thread