Messages in this thread Patch in this message | | | From | (Eric W. Biederman) | Date | Thu, 05 Aug 2021 11:48:43 -0500 | Subject | Re: [PATCH v3] ucounts: add missing data type changes |
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Nathan Chancellor <nathan@kernel.org> writes:
> Hi Eric, > > On 8/4/2021 12:47 PM, Eric W. Biederman wrote: >> Nathan Chancellor <nathan@kernel.org> writes: >> >>> On Fri, Jul 30, 2021 at 08:28:54AM +0200, Sven Schnelle wrote: >>>> commit f9c82a4ea89c3 ("Increase size of ucounts to atomic_long_t") >>>> changed the data type of ucounts/ucounts_max to long, but missed to >>>> adjust a few other places. This is noticeable on big endian platforms >>>> from user space because the /proc/sys/user/max_*_names files all >>>> contain 0. >>>> >>>> Fixes: f9c82a4ea89c ("Increase size of ucounts to atomic_long_t") >>>> Signed-off-by: Sven Schnelle <svens@linux.ibm.com> >>> >>> This patch in -next as commit e43fc41d1f7f ("ucounts: add missing data type >>> changes") causes Windows Subsystem for Linux to fail to start: >>> >>> [error 0x8007010b when launching `wsl.exe -d Arch'] Could not access starting >>> directory "\\wsl$\Arch\home\nathan" >>> >>> Specifically, it is the change to max_user_watches in >>> fs/notify/inotify/inotify_user.c, as the below diff gets me back to working. >>> Unfortunately, I have no additional information to offer beyond that as WSL's >>> init is custom and closed source (as far as I am aware) and there are no real >>> debugging utilities. >> >> Could you try this patch and tell us what value is being set? >> >> The only think I can imagine is that someone wants unlimited watches and >> sets the value to a ridiculously large value and the interpretation of >> that value winds up being different between int and long. >> >> This should allow you to read either dmesg or the kernel's log as it >> boots up and see what value is being written. From there it should >> be relatively straight forward to figure out what is going on. > > I applied this diff on top of mine and running 'dmesg |& grep intvec' shows: > > [ 0.282500] intvec: dmesg_restrict <- 0 > [ 0.282510] intvec: max_user_watches <- 524288 > > This seems much smaller than INT_MAX so I am not sure how the value could be > different between int and long but I am not at all familiar with the sysctl > code. > > More than happy to continue to test debug patches or provide any additional > information as I can.
Yes. Very strange.
Could you perhaps try the instrumenting proc_doulongvec_minmax the same way and see what is written in the failing case?
While looking at the code I did see one other serious bug. The min and max values are int constants intstead of long constants.
Could you test the change below and see if it makes a difference?
Eric
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 6576657a1a25..28b67cb9458d 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -54,6 +54,9 @@ static int fanotify_max_queued_events __read_mostly; #include <linux/sysctl.h> +static long ft_zero = 0; +static long ft_int_max = INT_MAX; + struct ctl_table fanotify_table[] = { { .procname = "max_user_groups", @@ -61,8 +64,8 @@ struct ctl_table fanotify_table[] = { .maxlen = sizeof(long), .mode = 0644, .proc_handler = proc_doulongvec_minmax, - .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_INT_MAX, + .extra1 = &ft_zero, + .extra2 = &ft_int_max, }, { .procname = "max_user_marks", @@ -70,8 +73,8 @@ struct ctl_table fanotify_table[] = { .maxlen = sizeof(long), .mode = 0644, .proc_handler = proc_doulongvec_minmax, - .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_INT_MAX, + .extra1 = &ft_zero, + .extra2 = &ft_int_max, }, { .procname = "max_queued_events", diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index 55fe7cdea2fb..62051247f6d2 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -55,6 +55,9 @@ struct kmem_cache *inotify_inode_mark_cachep __read_mostly; #include <linux/sysctl.h> +static long it_zero = 0; +static long it_int_max = INT_MAX; + struct ctl_table inotify_table[] = { { .procname = "max_user_instances", @@ -62,8 +65,8 @@ struct ctl_table inotify_table[] = { .maxlen = sizeof(long), .mode = 0644, .proc_handler = proc_doulongvec_minmax, - .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_INT_MAX, + .extra1 = &it_zero, + .extra2 = &it_int_max, }, { .procname = "max_user_watches", @@ -71,8 +74,8 @@ struct ctl_table inotify_table[] = { .maxlen = sizeof(long), .mode = 0644, .proc_handler = proc_doulongvec_minmax, - .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_INT_MAX, + .extra1 = &it_zero, + .extra2 = &it_int_max, }, { .procname = "max_queued_events", diff --git a/kernel/ucount.c b/kernel/ucount.c index 260ae7da815f..bb51849e6375 100644 --- a/kernel/ucount.c +++ b/kernel/ucount.c @@ -58,14 +58,17 @@ static struct ctl_table_root set_root = { .permissions = set_permissions, }; +static long ue_zero = 0; +static long ue_int_max = INT_MAX; + #define UCOUNT_ENTRY(name) \ { \ .procname = name, \ .maxlen = sizeof(long), \ .mode = 0644, \ .proc_handler = proc_doulongvec_minmax, \ - .extra1 = SYSCTL_ZERO, \ - .extra2 = SYSCTL_INT_MAX, \ + .extra1 = &ue_zero, \ + .extra2 = &ue_int_max, \ } static struct ctl_table user_table[] = { UCOUNT_ENTRY("max_user_namespaces"),
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