FAILED: patch "[PATCH] erofs: fix the out-of-bounds nameoff handling for trailing" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] erofs: fix the out-of-bounds nameoff handling for trailing" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x d18a3b5d337fa412a38e776e6b4b857a58836575
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026050132-undercoat-undercoat-0f5b@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d18a3b5d337fa412a38e776e6b4b857a58836575 Mon Sep 17 00:00:00 2001
From: Gao Xiang <xiang@kernel.org>
Date: Tue, 21 Apr 2026 15:59:52 +0800
Subject: [PATCH] erofs: fix the out-of-bounds nameoff handling for trailing
 dirents

Currently we already have boundary-checks for nameoffs, but the trailing
dirents are special since the namelens are calculated with strnlen()
with unchecked nameoffs.

If a crafted EROFS has a trailing dirent with nameoff >= maxsize,
maxsize - nameoff can underflow, causing strnlen() to read past the
directory block.

nameoff0 should also be verified to be a multiple of
`sizeof(struct erofs_dirent)` as well [1].

[1] https://sashiko.dev/#/patchset/20260416063511.3173774-1-hsiangkao%40linux.alibaba.com

Fixes: 3aa8ec716e52 ("staging: erofs: add directory operations")
Fixes: 33bac912840f ("staging: erofs: keep corrupted fs from crashing kernel in erofs_readdir()")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Reported-by: Junrui Luo <moonafterrain@outlook.com>
Closes: https://lore.kernel.org/r/A0FD7E0F-7558-49B0-8BC8-EB1ECDB2479A@outlook.com
Cc: stable@vger.kernel.org
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>

diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
index e5132575b9d3..4aa52a5f204a 100644
--- a/fs/erofs/dir.c
+++ b/fs/erofs/dir.c
@@ -19,20 +19,18 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
 		const char *de_name = (char *)dentry_blk + nameoff;
 		unsigned int de_namelen;
 
-		/* the last dirent in the block? */
-		if (de + 1 >= end)
-			de_namelen = strnlen(de_name, maxsize - nameoff);
-		else
+		/* non-trailing dirent in the directory block? */
+		if (de + 1 < end)
 			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
+		else if (maxsize <= nameoff)
+			goto err_bogus;
+		else
+			de_namelen = strnlen(de_name, maxsize - nameoff);
 
-		/* a corrupted entry is found */
-		if (nameoff + de_namelen > maxsize ||
-		    de_namelen > EROFS_NAME_LEN) {
-			erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
-				  EROFS_I(dir)->nid);
-			DBG_BUGON(1);
-			return -EFSCORRUPTED;
-		}
+		/* a corrupted entry is found (including negative namelen) */
+		if (!in_range32(de_namelen, 1, EROFS_NAME_LEN) ||
+		    nameoff + de_namelen > maxsize)
+			goto err_bogus;
 
 		if (!dir_emit(ctx, de_name, de_namelen,
 			      erofs_nid_to_ino64(EROFS_SB(dir->i_sb),
@@ -42,6 +40,10 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
 		ctx->pos += sizeof(struct erofs_dirent);
 	}
 	return 0;
+err_bogus:
+	erofs_err(dir->i_sb, "bogus dirent @ nid %llu", EROFS_I(dir)->nid);
+	DBG_BUGON(1);
+	return -EFSCORRUPTED;
 }
 
 static int erofs_readdir(struct file *f, struct dir_context *ctx)
@@ -88,7 +90,7 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
 		}
 
 		nameoff = le16_to_cpu(de->nameoff);
-		if (nameoff < sizeof(struct erofs_dirent) || nameoff >= bsz) {
+		if (!nameoff || nameoff >= bsz || (nameoff % sizeof(*de))) {
 			erofs_err(sb, "invalid de[0].nameoff %u @ nid %llu",
 				  nameoff, EROFS_I(dir)->nid);
 			err = -EFSCORRUPTED;

[PATCH 5.15.y] erofs: fix the out-of-bounds nameoff handling for trailing dirents

[Sasha Levin]

From: Gao Xiang <hsiangkao@linux.alibaba.com>

[ Upstream commit d18a3b5d337fa412a38e776e6b4b857a58836575 ]

Currently we already have boundary-checks for nameoffs, but the trailing
dirents are special since the namelens are calculated with strnlen()
with unchecked nameoffs.

If a crafted EROFS has a trailing dirent with nameoff >= maxsize,
maxsize - nameoff can underflow, causing strnlen() to read past the
directory block.

nameoff0 should also be verified to be a multiple of
`sizeof(struct erofs_dirent)` as well [1].

[1] https://sashiko.dev/#/patchset/20260416063511.3173774-1-hsiangkao%40linux.alibaba.com

Fixes: 3aa8ec716e52 ("staging: erofs: add directory operations")
Fixes: 33bac912840f ("staging: erofs: keep corrupted fs from crashing kernel in erofs_readdir()")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Reported-by: Junrui Luo <moonafterrain@outlook.com>
Closes: https://lore.kernel.org/r/A0FD7E0F-7558-49B0-8BC8-EB1ECDB2479A@outlook.com
Cc: stable@vger.kernel.org
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
[ replaced upstream `bsz` with `PAGE_SIZE` and `sizeof(*de)` with `sizeof(struct erofs_dirent)` ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/erofs/dir.c | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
index eee9b0b31b639..ac140587505b5 100644
--- a/fs/erofs/dir.c
+++ b/fs/erofs/dir.c
@@ -37,20 +37,18 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
 		nameoff = le16_to_cpu(de->nameoff);
 		de_name = (char *)dentry_blk + nameoff;
 
-		/* the last dirent in the block? */
-		if (de + 1 >= end)
-			de_namelen = strnlen(de_name, maxsize - nameoff);
-		else
+		/* non-trailing dirent in the directory block? */
+		if (de + 1 < end)
 			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
+		else if (maxsize <= nameoff)
+			goto err_bogus;
+		else
+			de_namelen = strnlen(de_name, maxsize - nameoff);
 
-		/* a corrupted entry is found */
-		if (nameoff + de_namelen > maxsize ||
-		    de_namelen > EROFS_NAME_LEN) {
-			erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
-				  EROFS_I(dir)->nid);
-			DBG_BUGON(1);
-			return -EFSCORRUPTED;
-		}
+		/* a corrupted entry is found (including negative namelen) */
+		if (!in_range32(de_namelen, 1, EROFS_NAME_LEN) ||
+		    nameoff + de_namelen > maxsize)
+			goto err_bogus;
 
 		debug_one_dentry(d_type, de_name, de_namelen);
 		if (!dir_emit(ctx, de_name, de_namelen,
@@ -62,6 +60,10 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
 	}
 	*ofs = maxsize;
 	return 0;
+err_bogus:
+	erofs_err(dir->i_sb, "bogus dirent @ nid %llu", EROFS_I(dir)->nid);
+	DBG_BUGON(1);
+	return -EFSCORRUPTED;
 }
 
 static int erofs_readdir(struct file *f, struct dir_context *ctx)
@@ -95,8 +97,8 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
 
 		nameoff = le16_to_cpu(de->nameoff);
 
-		if (nameoff < sizeof(struct erofs_dirent) ||
-		    nameoff >= PAGE_SIZE) {
+		if (!nameoff || nameoff >= PAGE_SIZE ||
+		    (nameoff % sizeof(struct erofs_dirent))) {
 			erofs_err(dir->i_sb,
 				  "invalid de[0].nameoff %u @ nid %llu",
 				  nameoff, EROFS_I(dir)->nid);
-- 
2.53.0

Re: [PATCH 5.15.y] erofs: fix the out-of-bounds nameoff handling for trailing dirents

[Gao Xiang]

On 2026/5/2 02:48, Sasha Levin wrote:
> From: Gao Xiang <hsiangkao@linux.alibaba.com>
> 
> [ Upstream commit d18a3b5d337fa412a38e776e6b4b857a58836575 ]
> 
> Currently we already have boundary-checks for nameoffs, but the trailing
> dirents are special since the namelens are calculated with strnlen()
> with unchecked nameoffs.
> 
> If a crafted EROFS has a trailing dirent with nameoff >= maxsize,
> maxsize - nameoff can underflow, causing strnlen() to read past the
> directory block.
> 
> nameoff0 should also be verified to be a multiple of
> `sizeof(struct erofs_dirent)` as well [1].
> 
> [1] https://sashiko.dev/#/patchset/20260416063511.3173774-1-hsiangkao%40linux.alibaba.com
> 
> Fixes: 3aa8ec716e52 ("staging: erofs: add directory operations")
> Fixes: 33bac912840f ("staging: erofs: keep corrupted fs from crashing kernel in erofs_readdir()")
> Reported-by: Yuhao Jiang <danisjiang@gmail.com>
> Reported-by: Junrui Luo <moonafterrain@outlook.com>
> Closes: https://lore.kernel.org/r/A0FD7E0F-7558-49B0-8BC8-EB1ECDB2479A@outlook.com
> Cc: stable@vger.kernel.org
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> Reviewed-by: Chao Yu <chao@kernel.org>
> [ replaced upstream `bsz` with `PAGE_SIZE` and `sizeof(*de)` with `sizeof(struct erofs_dirent)` ]
> Signed-off-by: Sasha Levin <sashal@kernel.org>
Looks good to me.

Thanks,
Gao Xiang