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Al Viro 16a58e9a17 fix proc_sys_compare() handling of in-lookup dentries ... [ Upstream commit b969f9614885c20f903e1d1f9445611daf161d6d ] There's one case where ->d_compare() can be called for an in-lookup dentry; usually that's nothing special from ->d_compare() point of view, but... proc_sys_compare() is weird. The thing is, /proc/sys subdirectories can look differently for different processes. Up to and including having the same name resolve to different dentries - all of them hashed. The way it's done is ->d_compare() refusing to admit a match unless this dentry is supposed to be visible to this caller. The information needed to discriminate between them is stored in inode; it is set during proc_sys_lookup() and until it's done d_splice_alias() we really can't tell who should that dentry be visible for. Normally there's no negative dentries in /proc/sys; we can run into a dying dentry in RCU dcache lookup, but those can be safely rejected. However, ->d_compare() is also called for in-lookup dentries, before they get positive - or hashed, for that matter. In case of match we will wait until dentry leaves in-lookup state and repeat ->d_compare() afterwards. In other words, the right behaviour is to treat the name match as sufficient for in-lookup dentries; if dentry is not for us, we'll see that when we recheck once proc_sys_lookup() is done with it. While we are at it, fix the misspelled READ_ONCE and WRITE_ONCE there. Fixes: d9171b9345 ("parallel lookups machinery, part 4 (and last)") Reported-by: NeilBrown <neilb@brown.name> Reviewed-by: Christian Brauner <brauner@kernel.org> Reviewed-by: NeilBrown <neil@brown.name> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Sasha Levin <sashal@kernel.org>		2025-07-17 18:25:01 +02:00
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array.c
base.c	fs/procfs: fix the comment above proc_pid_wchan()	2025-04-10 14:29:42 +02:00
cmdline.c
consoles.c
cpuinfo.c
devices.c
fd.c
fd.h
generic.c
inode.c	fix proc_sys_compare() handling of in-lookup dentries	2025-07-17 18:25:01 +02:00
internal.h
interrupts.c
Kconfig
kcore.c
kmsg.c
loadavg.c
Makefile
meminfo.c
namespaces.c
nommu.c
page.c
proc_net.c
proc_sysctl.c	fix proc_sys_compare() handling of in-lookup dentries	2025-07-17 18:25:01 +02:00
proc_tty.c
root.c
self.c
softirqs.c	proc/softirqs: replace seq_printf with seq_put_decimal_ull_width	2024-12-14 19:44:21 +01:00
stat.c
task_mmu.c
task_nommu.c
thread_self.c
uptime.c
util.c
version.c
vmcore.c	fs/proc: fix softlockup in __read_vmcore (part 2)	2025-02-01 18:18:51 +01:00