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[2403:580d:fda1:0:2bb5:f164:6e6a:38d8]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2beb0e64b96sm2596605ad.17.2026.05.21.15.13.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 May 2026 15:13:04 -0700 (PDT) Message-ID: Date: Fri, 22 May 2026 07:43:00 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs() To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org References: Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/5/22 00:37, fdmanana@kernel.org 写道: > From: Filipe Manana > > In the beginning of the loop, we try to obtain a locked delayed ref head, > if 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(), > which can return an error pointer. If the error pointer is -EAGAIN we do > a continue and go back to the beginning of the loop, which will not try > again to call btrfs_select_ref_head() since 'locked_ref' is no longer > NULL but it's ERR_PTR(-EAGAIN), and then we do: > > spin_lock(&locked_ref->lock); > > against a ERR_PTR(-EAGAIN) value, generating an invalid pointer > dereference. > > Fix this by ensuring that 'locked_ref' is set to NULL when > btrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count' > as well, to prevent infinite looping. We do this by doing a goto to the > bottom of the loop that already sets 'locked_ref' to NULL and does a > cond_resched(), with an increment to 'count' right before the goto. > These measures were in place before the refactoring in commit 0110a4c43451 > ("btrfs: refactor __btrfs_run_delayed_refs loop") but were unintentionally > lost afterwards. > > Reported-by: Dan Carpenter > Link: https://lore.kernel.org/linux-btrfs/ag8ARRwykv8bpJ87@stanley.mountain/ > Fixes: 0110a4c43451 ("btrfs: refactor __btrfs_run_delayed_refs loop") > Signed-off-by: Filipe Manana Reviewed-by: Qu Wenruo Thanks, Qu > --- > > V2: Use a goto approach to jump to the bottom of the loop, that already > sets locked_ref to NULL and does a cond_resched() too. > > fs/btrfs/extent-tree.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index ecc1acb1e340..6030cdbdb742 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -2108,7 +2108,8 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, > locked_ref = btrfs_select_ref_head(fs_info, delayed_refs); > if (IS_ERR_OR_NULL(locked_ref)) { > if (PTR_ERR(locked_ref) == -EAGAIN) { > - continue; > + count++; > + goto again; > } else { > break; > } > @@ -2156,7 +2157,7 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, > * Either success case or btrfs_run_delayed_refs_for_head > * returned -EAGAIN, meaning we need to select another head > */ > - > +again: > locked_ref = NULL; > cond_resched(); > } while ((min_bytes != U64_MAX && bytes_processed < min_bytes) ||