#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@xxxxxxxxxxxxxxxxxxxxxxxxx Link: https://lore.kernel.org/linux-mm/000000000000273d0105ff97bf56@xxxxxxxxxx/ Signed-off-by: David Howells <dhowells@xxxxxxxxxx> cc: Sven Schnelle <svens@xxxxxxxxxxxxx> cc: akpm@xxxxxxxxxxxxxxxxxxxx cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> cc: "David S. Miller" <davem@xxxxxxxxxxxxx> cc: Jeff Layton <jlayton@xxxxxxxxxx> cc: Steve French <sfrench@xxxxxxxxx> cc: Shyam Prasad N <nspmangalore@xxxxxxxxx> cc: Rohith Surabattula <rohiths.msft@xxxxxxxxx> cc: Jens Axboe <axboe@xxxxxxxxx> cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> cc: "David S. Miller" <davem@xxxxxxxxxxxxx> cc: Eric Dumazet <edumazet@xxxxxxxxxx> cc: Jakub Kicinski <kuba@xxxxxxxxxx> cc: Paolo Abeni <pabeni@xxxxxxxxxx> cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> cc: linux-mm@xxxxxxxxx cc: linux-crypto@xxxxxxxxxxxxxxx cc: linux-cachefs@xxxxxxxxxx cc: linux-cifs@xxxxxxxxxxxxxxx cc: linux-fsdevel@xxxxxxxxxxxxxxx cc: netdev@xxxxxxxxxxxxxxx --- 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; }