Hello,
syzbot found the following issue on:
HEAD commit: 56e337f2cf13 Revert "gpio: Revert regression in sysfs-gpio..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17e0a8c5700000
kernel config: https://syzkaller.appspot.com/x/.config?x=d35f9bc6884af6c9
dashboard link: https://syzkaller.appspot.com/bug?extid=d55757faa9b80590767b
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=134e4e91700000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=127bd083700000
Bisection is inconclusive: the issue happens on the oldest tested release.
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=138601c5700000
final oops: https://syzkaller.appspot.com/x/report.txt?x=104601c5700000
console output: https://syzkaller.appspot.com/x/log.txt?x=178601c5700000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffc794ecea0 R14: 000000000000000d R15: 00007ff328525490
</TASK>
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:71 [inline]
BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: null-ptr-deref in page_ref_count include/linux/page_ref.h:67 [inline]
BUG: KASAN: null-ptr-deref in put_page_testzero include/linux/mm.h:717 [inline]
BUG: KASAN: null-ptr-deref in __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
Read of size 4 at addr 0000000000000034 by task syz-executor168/3599
CPU: 1 PID: 3599 Comm: syz-executor168 Not tainted 5.17.0-rc8-syzkaller-00003-g56e337f2cf13 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
__kasan_report mm/kasan/report.c:446 [inline]
kasan_report.cold+0x66/0xdf mm/kasan/report.c:459
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
instrument_atomic_read include/linux/instrumented.h:71 [inline]
atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
page_ref_count include/linux/page_ref.h:67 [inline]
put_page_testzero include/linux/mm.h:717 [inline]
__free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
watch_queue_set_size+0x499/0x630 kernel/watch_queue.c:275
pipe_ioctl+0xac/0x2b0 fs/pipe.c:632
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7ff3284b2d59
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 31 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc794ece38 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000031 RCX: 00007ff3284b2d59
RDX: 0000000000000029 RSI: 0000000000005760 RDI: 0000000000000003
RBP: 00007ffc794ece40 R08: 0000000000000001 R09: 00007ffc794e0035
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffc794ecea0 R14: 000000000000000d R15: 00007ff328525490
</TASK>
==================================================================
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email protected].
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches
On domenica 20 marzo 2022 23:04:18 CET syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 56e337f2cf13 Revert "gpio: Revert regression in sysfs-gpio..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17e0a8c5700000
> kernel config: https://syzkaller.appspot.com/x/.config?x=d35f9bc6884af6c9
> dashboard link: https://syzkaller.appspot.com/bug?extid=d55757faa9b80590767b
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=134e4e91700000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=127bd083700000
>
> Bisection is inconclusive: the issue happens on the oldest tested release.
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=138601c5700000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=104601c5700000
> console output: https://syzkaller.appspot.com/x/log.txt?x=178601c5700000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
>
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffc794ecea0 R14: 000000000000000d R15: 00007ff328525490
> </TASK>
> ==================================================================
> BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:71 [inline]
> BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
> BUG: KASAN: null-ptr-deref in page_ref_count include/linux/page_ref.h:67 [inline]
> BUG: KASAN: null-ptr-deref in put_page_testzero include/linux/mm.h:717 [inline]
> BUG: KASAN: null-ptr-deref in __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
> Read of size 4 at addr 0000000000000034 by task syz-executor168/3599
>
> CPU: 1 PID: 3599 Comm: syz-executor168 Not tainted 5.17.0-rc8-syzkaller-00003-g56e337f2cf13 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> __kasan_report mm/kasan/report.c:446 [inline]
> kasan_report.cold+0x66/0xdf mm/kasan/report.c:459
> check_region_inline mm/kasan/generic.c:183 [inline]
> kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
> instrument_atomic_read include/linux/instrumented.h:71 [inline]
> atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
> page_ref_count include/linux/page_ref.h:67 [inline]
> put_page_testzero include/linux/mm.h:717 [inline]
> __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
> watch_queue_set_size+0x499/0x630 kernel/watch_queue.c:275
> pipe_ioctl+0xac/0x2b0 fs/pipe.c:632
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:874 [inline]
> __se_sys_ioctl fs/ioctl.c:860 [inline]
> __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7ff3284b2d59
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 31 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffc794ece38 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000031 RCX: 00007ff3284b2d59
> RDX: 0000000000000029 RSI: 0000000000005760 RDI: 0000000000000003
> RBP: 00007ffc794ece40 R08: 0000000000000001 R09: 00007ffc794e0035
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffc794ecea0 R14: 000000000000000d R15: 00007ff328525490
> </TASK>
> ==================================================================
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at [email protected].
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/000000000000b1807c05daad8f98%40google.com.
>
Sorry, left an open brace and compilation failed.
Let's try again...
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Fabio M. De Francesco
Fabio M. De Francesco <[email protected]> wrote:
> I cannot have any objection, it's up to you to decide :)
Of course you can object. That's kind of the point of a review;-)
How about the attached instead, then?
David
---
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -271,9 +271,8 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
return 0;
error_p:
- for (i = 0; i < nr_pages; i++)
- if (pages[i])
- __free_page(pages[i]);
+ while (--i >= 0)
+ __free_page(pages[i]);
kfree(pages);
error:
(void) account_pipe_buffers(pipe->user, nr_pages, pipe->nr_accounted);
Hi Fabio,
How about using my patch instead? I wonder if __free_pages() should check for
a NULL pages pointer...
David
---
watch_queue: Fix NULL dereference in error cleanup
In watch_queue_set_size(), the error cleanup code doesn't take account of
the fact that __free_page() can't handle a NULL pointer when trying to free
up buffer pages that did get allocated.
Fix this by only calling __free_page() on non-NULL pointers extracted from
the list (the list was allocated by kcalloc() so was pre-cleared).
Without the fix, this can lead to something like the following:
BUG: KASAN: null-ptr-deref in __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
Read of size 4 at addr 0000000000000034 by task syz-executor168/3599
...
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
__kasan_report mm/kasan/report.c:446 [inline]
kasan_report.cold+0x66/0xdf mm/kasan/report.c:459
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
instrument_atomic_read include/linux/instrumented.h:71 [inline]
atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
page_ref_count include/linux/page_ref.h:67 [inline]
put_page_testzero include/linux/mm.h:717 [inline]
__free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
watch_queue_set_size+0x499/0x630 kernel/watch_queue.c:275
pipe_ioctl+0xac/0x2b0 fs/pipe.c:632
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-and-tested-by: [email protected]
Signed-off-by: David Howells <[email protected]>
---
kernel/watch_queue.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index 00703444a219..09f35bab496e 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -272,7 +272,8 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
error_p:
for (i = 0; i < nr_pages; i++)
- __free_page(pages[i]);
+ if (pages[i])
+ __free_page(pages[i]);
kfree(pages);
error:
(void) account_pipe_buffers(pipe->user, nr_pages, pipe->nr_accounted);
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git 733021c6d8607c5c5ab08bbe9b400d0da609185f
Hello,
syzbot has tested the proposed patch and the reproducer did not trigger any issue:
Reported-and-tested-by: [email protected]
Tested on:
commit: f443e374 Linux 5.17
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=19ca6f72fd444749
dashboard link: https://syzkaller.appspot.com/bug?extid=d55757faa9b80590767b
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch: https://syzkaller.appspot.com/x/patch.diff?x=15ec554d700000
Note: testing is done by a robot and is best-effort only.
On luned? 21 marzo 2022 09:46:51 CET David Howells wrote:
> Hi Fabio,
>
> How about using my patch instead? I wonder if __free_pages() should check for
> a NULL pages pointer...
>
> David
> ---
> watch_queue: Fix NULL dereference in error cleanup
>
> In watch_queue_set_size(), the error cleanup code doesn't take account of
> the fact that __free_page() can't handle a NULL pointer when trying to free
> up buffer pages that did get allocated.
>
> Fix this by only calling __free_page() on non-NULL pointers extracted from
> the list (the list was allocated by kcalloc() so was pre-cleared).
>
> Without the fix, this can lead to something like the following:
>
> BUG: KASAN: null-ptr-deref in __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
> Read of size 4 at addr 0000000000000034 by task syz-executor168/3599
> ...
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> __kasan_report mm/kasan/report.c:446 [inline]
> kasan_report.cold+0x66/0xdf mm/kasan/report.c:459
> check_region_inline mm/kasan/generic.c:183 [inline]
> kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
> instrument_atomic_read include/linux/instrumented.h:71 [inline]
> atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
> page_ref_count include/linux/page_ref.h:67 [inline]
> put_page_testzero include/linux/mm.h:717 [inline]
> __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
> watch_queue_set_size+0x499/0x630 kernel/watch_queue.c:275
> pipe_ioctl+0xac/0x2b0 fs/pipe.c:632
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:874 [inline]
> __se_sys_ioctl fs/ioctl.c:860 [inline]
> __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> Fixes: c73be61cede5 ("pipe: Add general notification queue support")
> Reported-and-tested-by: [email protected]
> Signed-off-by: David Howells <[email protected]>
> ---
> kernel/watch_queue.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
> index 00703444a219..09f35bab496e 100644
> --- a/kernel/watch_queue.c
> +++ b/kernel/watch_queue.c
> @@ -272,7 +272,8 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
>
> error_p:
> for (i = 0; i < nr_pages; i++)
> - __free_page(pages[i]);
> + if (pages[i])
> + __free_page(pages[i]);
> kfree(pages);
> error:
> (void) account_pipe_buffers(pipe->user, nr_pages, pipe->nr_accounted);
>
>
I cannot have any objection, it's up to you to decide :)
I just noticed that you now have two tests in one loop:
the first is for the index less than an unnecessary high value:
the second is for pages[i] being NULL.
However, I have no other objections. Please use your patch instead.
Thanks,
Fabio M. De Francesco
On domenica 20 marzo 2022 23:04:18 CET syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 56e337f2cf13 Revert "gpio: Revert regression in sysfs-gpio..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17e0a8c5700000
> kernel config: https://syzkaller.appspot.com/x/.config?x=d35f9bc6884af6c9
> dashboard link: https://syzkaller.appspot.com/bug?extid=d55757faa9b80590767b
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=134e4e91700000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=127bd083700000
>
> Bisection is inconclusive: the issue happens on the oldest tested release.
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=138601c5700000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=104601c5700000
> console output: https://syzkaller.appspot.com/x/log.txt?x=178601c5700000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
>
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffc794ecea0 R14: 000000000000000d R15: 00007ff328525490
> </TASK>
> ==================================================================
> BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:71 [inline]
> BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
> BUG: KASAN: null-ptr-deref in page_ref_count include/linux/page_ref.h:67 [inline]
> BUG: KASAN: null-ptr-deref in put_page_testzero include/linux/mm.h:717 [inline]
> BUG: KASAN: null-ptr-deref in __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
> Read of size 4 at addr 0000000000000034 by task syz-executor168/3599
>
> CPU: 1 PID: 3599 Comm: syz-executor168 Not tainted 5.17.0-rc8-syzkaller-00003-g56e337f2cf13 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> __kasan_report mm/kasan/report.c:446 [inline]
> kasan_report.cold+0x66/0xdf mm/kasan/report.c:459
> check_region_inline mm/kasan/generic.c:183 [inline]
> kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
> instrument_atomic_read include/linux/instrumented.h:71 [inline]
> atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
> page_ref_count include/linux/page_ref.h:67 [inline]
> put_page_testzero include/linux/mm.h:717 [inline]
> __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
> watch_queue_set_size+0x499/0x630 kernel/watch_queue.c:275
> pipe_ioctl+0xac/0x2b0 fs/pipe.c:632
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:874 [inline]
> __se_sys_ioctl fs/ioctl.c:860 [inline]
> __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7ff3284b2d59
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 31 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffc794ece38 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000031 RCX: 00007ff3284b2d59
> RDX: 0000000000000029 RSI: 0000000000005760 RDI: 0000000000000003
> RBP: 00007ffc794ece40 R08: 0000000000000001 R09: 00007ffc794e0035
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007ffc794ecea0 R14: 000000000000000d R15: 00007ff328525490
> </TASK>
> ==================================================================
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at [email protected].
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/000000000000b1807c05daad8f98%40google.com.
>
Probably I'm missing something, but I want to try once more...
The argument I follow is that when, in the "error_p" label, the code
frees the pages, it frees in a loop from pages[0] to pages[nr_pages -1].
Thus I saw that when pages[i] are allocated at line 256 by a call to
alloc_page() and this allocation fails it jumps to the "error_p" label
without saving and using the number of successful allocations as a limit
of the loop that calls __free_pages().
As I said, perhaps I'm missing something deeper but I noticed that in my
diff I assigned "allocated_pages" with "i + 1" and probably I'm still
going off by one.
Let's try the last time...
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Thanks,
Fabio M. De Francesco