device/linux-huawei-y530: fix lookup of symbolic links (!856)

device/linux-huawei-y530/10_vfs-fix-proc-tid-fdinfo-fd-file-handling.patch

@@ -0,0 +1,80 @@
+From 562eac4226c2cf8718b8d87fc947545ccbb6dd20 Mon Sep 17 00:00:00 2001
+From: Linus Torvalds <torvalds@linux-foundation.org>
+Date: Mon, 4 Jun 2012 11:00:45 -0700
+Subject: [PATCH] vfs: Fix /proc/<tid>/fdinfo/<fd> file handling
+
+Cyrill Gorcunov reports that I broke the fdinfo files with commit
+30a08bf2d31d ("proc: move fd symlink i_mode calculations into
+tid_fd_revalidate()"), and he's quite right.
+
+The tid_fd_revalidate() function is not just used for the <tid>/fd
+symlinks, it's also used for the <tid>/fdinfo/<fd> files, and the
+permission model for those are different.
+
+So do the dynamic symlink permission handling just for symlinks, making
+the fdinfo files once more appear as the proper regular files they are.
+
+Of course, Al Viro argued (probably correctly) that we shouldn't do the
+symlink permission games at all, and make the symlinks always just be
+the normal 'lrwxrwxrwx'.  That would have avoided this issue too, but
+since somebody noticed that the permissions had changed (which was the
+reason for that original commit 30a08bf2d31d in the first place), people
+do apparently use this feature.
+
+[ Basically, you can use the symlink permission data as a cheap "fdinfo"
+  replacement, since you see whether the file is open for reading and/or
+  writing by just looking at st_mode of the symlink.  So the feature
+  does make sense, even if the pain it has caused means we probably
+  shouldn't have done it to begin with. ]
+
+Reported-and-tested-by: Cyrill Gorcunov <gorcunov@openvz.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+---
+ fs/proc/base.c | 17 ++++++++++-------
+ 1 file changed, 10 insertions(+), 7 deletions(-)
+
+diff --git a/fs/proc/base.c b/fs/proc/base.c
+index 2f198dad..c8cb15dc 100644
+--- a/fs/proc/base.c
++++ b/fs/proc/base.c
+@@ -1838,7 +1838,7 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
+ 			rcu_read_lock();
+ 			file = fcheck_files(files, fd);
+ 			if (file) {
+-				unsigned i_mode, f_mode = file->f_mode;
++				unsigned f_mode = file->f_mode;
+ 
+ 				rcu_read_unlock();
+ 				put_files_struct(files);
+@@ -1854,12 +1854,14 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
+ 					inode->i_gid = 0;
+ 				}
+ 
+-				i_mode = S_IFLNK;
+-				if (f_mode & FMODE_READ)
+-					i_mode |= S_IRUSR | S_IXUSR;
+-				if (f_mode & FMODE_WRITE)
+-					i_mode |= S_IWUSR | S_IXUSR;
+-				inode->i_mode = i_mode;
++				if (S_ISLNK(inode->i_mode)) {
++					unsigned i_mode = S_IFLNK;
++					if (f_mode & FMODE_READ)
++						i_mode |= S_IRUSR | S_IXUSR;
++					if (f_mode & FMODE_WRITE)
++						i_mode |= S_IWUSR | S_IXUSR;
++					inode->i_mode = i_mode;
++				}
+ 
+ 				security_task_to_inode(task, inode);
+ 				put_task_struct(task);
+@@ -1894,6 +1896,7 @@ static struct dentry *proc_fd_instantiate(struct inode *dir,
+ 	ei = PROC_I(inode);
+ 	ei->fd = fd;
+ 
++	inode->i_mode = S_IFLNK;
+ 	inode->i_op = &proc_pid_link_inode_operations;
+ 	inode->i_size = 64;
+ 	ei->op.proc_get_link = proc_fd_link;
+-- 
+2.17.1
+

device/linux-huawei-y530/APKBUILD

@@ -2,7 +2,7 @@
 
 pkgname="linux-huawei-y530"
 pkgver=3.4.0
-pkgrel=7
+pkgrel=8
 pkgdesc="Kernel for Huawei MSM8x1x devices"
 arch="armv7"
 _carch="arm"
@@ -39,6 +39,7 @@ source="
 	07_fix_mdss_fb_refresh_rate.patch
 	08_fix_touchscreen.patch
 	09_fix_various_include_directives.patch
+	10_vfs-fix-proc-tid-fdinfo-fd-file-handling.patch
 "
 builddir="$srcdir/${_repository}-${_commit}"
 
@@ -121,4 +122,5 @@ fbc61e379403990167853f4c4fbdfa22d7e9661a7eedecf2a75eec2a8008991a82d0a61be844ab4b
 384ae0bf2f5d7e15b0b60655693fd600b52c0f5bfcaa4ba7336d0ebeb224e84b99b597f77d26a1249e14a4e7bbc1629be00556b393bb9dd2266cb4bd67c3cfea  06_fix_mdss_fb_rgb_mode.patch
 1f743d3e7f4ac7401167ea35edc7d7e113bd80824c4d53631d7500f33557ff486163f8244786c16506b2e21db6ccbcd8a0f7b26fcf4937efee50b62c074f9a22  07_fix_mdss_fb_refresh_rate.patch
 f83e9b6549155a2f32c89dffbab3ad6fba7b8d93976dfccb1232833244ed6e064e28105a321eaa934c5bb326384730d03f3d3141227a7258a30045fa12573268  08_fix_touchscreen.patch
-c9831aa037d4cb26fa349c44a27111daf8f7a84a9527d0221ecc4f01839b195243c178838663ff7592bb1d5c3cdc9872b449254beb7b9dffa67c365c3d8e042c  09_fix_various_include_directives.patch"
+c9831aa037d4cb26fa349c44a27111daf8f7a84a9527d0221ecc4f01839b195243c178838663ff7592bb1d5c3cdc9872b449254beb7b9dffa67c365c3d8e042c  09_fix_various_include_directives.patch
+b0b9bcea00ca4a79ea6d6a9e0b153559161a102b0856193c7d775318beeb1d4ffb194127bf8f94f006930dd7cd330c3185f9bd205fef39e9856ffe9019fc2a34  10_vfs-fix-proc-tid-fdinfo-fd-file-handling.patch"